diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7b6efa5..675e180 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,23 @@
 # Changelog
 
+## Unreleased
+
+App billing features; they need an Anikeen ID release that supports them.
+
+- Free trials: `trial_days` / `trial_ends_at` (optional `trial_once`, `trial_payment_method` with
+  `TrialPaymentMethod::REQUIRED` / `OPTIONAL`) when creating subscriptions and checkout sessions;
+  `Subscription::isTrial()`.
+- Discounts per billed period: `discount` with `percent_off` or `amount_off`, `duration` and `label`.
+- Plan changes of running subscriptions: `AppSubscription::change()` (`apply: now` or
+  `period_end`) and `AppSubscription::cancelScheduledChange()`.
+- App orders: order lines with subscription, period, net amount and discount;
+  `AppOrders::invoicePdf()`. Confirmable orders of trusted apps (`confirm: true`).
+- Billing portal links that work without a login: `createBillingPortalLinkForUser()` and
+  `appBillingPortalUrl()`.
+- Webhook events `subscription.trial_will_end`, `subscription.discount_ended`,
+  `subscription.updated` and `subscription.renewed` (`EventType::SUBSCRIPTION_*`);
+  `data.reason` with `CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD`.
+
 ## 3.2.0 (2026-11-06)
 
 Elapsed-period billing and user lookup; they need an Anikeen ID release that supports them.
diff --git a/README.md b/README.md
index af76b77..6dd2be9 100644
--- a/README.md
+++ b/README.md
@@ -382,8 +382,102 @@ same value as `status`):
 | `expired` | Paused and ran out; `resume()` starts a new period | no |
 | `cancelled` | Cancelled for good | no |
 
-There are shortcuts for each: `isDraft()`, `isPaused()`, `isCancelling()`, `isExpired()`,
-`isCancelled()`. App subscriptions (`appSubscriptions()`) have the same methods.
+There are shortcuts for each: `isDraft()`, `isTrial()`, `isPaused()`, `isCancelling()`,
+`isExpired()`, `isCancelled()`. App subscriptions (`appSubscriptions()`) have the same methods.
+
+#### Free trials
+
+Give a subscription a free trial with `trial_days` (1–365, counted from the user's confirmation or
+the checkout) or a fixed `trial_ends_at` (ISO 8601, in the future), not both. The subscription
+starts right away with `status` `trial` and nothing billed; the first period is billed when the
+trial ends. `trial_once` refuses the trial if the user already had one with your app in the same
+`group` (422 when creating, 409 `trial_already_used` when checking out):
+
+```php
+$subscription = $user->subscriptions()->create([
+    'name' => 'Pixel Stream Pass',
+    'unit' => 'month',
+    'price' => 6.714286,
+    'trial_days' => 14,
+    'trial_once' => true,
+]);
+```
+
+A few days before the trial ends, Anikeen ID sends `subscription.trial_will_end`
+(`EventType::SUBSCRIPTION_TRIAL_WILL_END`), e.g. to remind the user; `data.payment_method_missing`
+tells you whether the user still has to add a payment method. Cancelling during the trial
+bills nothing. Trials work the same for app subscriptions and per subscription of a checkout
+session.
+
+By default the user needs a payment method to confirm a trial. With `trial_payment_method`
+`TrialPaymentMethod::OPTIONAL` (only together with a trial; `TrialPaymentMethod::REQUIRED` is the
+default) the user can confirm it without one, as long as nothing else has to be paid: in a
+checkout session every subscription has to be such a trial. The confirmation page tells the user
+to add a payment method before the trial ends. If there is still none then, the subscription is
+**cancelled** at the trial's end instead of billed: `status` `cancelled`, `cancellation_reason`
+`CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD`, `subscription.cancelled` with
+`data.reason` set to the same value, and no `subscription.renewed`. Adding a payment method later
+doesn't bring it back – create a new subscription. The trial still counts for `trial_once`.
+Anikeen ID also mails the user a few days before such a trial ends without a payment method.
+
+```php
+use Anikeen\Id\Enums\CancellationReason;
+use Anikeen\Id\Enums\TrialPaymentMethod;
+use Anikeen\Id\Webhooks\EventType;
+
+$subscription = $user->appSubscriptions()->create([
+    'group' => $teamId,
+    'name' => 'Uptimr Pro',
+    'unit' => 'month',
+    'price' => 19.00,
+    'trial_days' => 14,
+    'trial_payment_method' => TrialPaymentMethod::OPTIONAL,
+]);
+
+// in your webhook handler
+$data = $event['data'];
+
+match ($event['type']) {
+    EventType::SUBSCRIPTION_TRIAL_WILL_END => $data['payment_method_missing']
+        ? Reminder::addPaymentMethod($data['object']['id'])
+        : null,
+    EventType::SUBSCRIPTION_CANCELLED => $data['reason'] === CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD
+        ? Pass::downgrade($data['object']['id'])
+        : Pass::revoke($data['object']['id']),
+    default => null,
+};
+```
+
+#### Discounts
+
+A `discount` (e.g. a coupon) lowers the price of billed periods: every discounted period gets a
+negative line with the `label` next to its usage on the same bill, until the discount ends.
+
+```php
+$subscription = $user->subscriptions()->create([
+    'name' => 'Pixel Stream Pass',
+    'unit' => 'month',
+    'price' => 6.714286,
+    'discount' => [
+        'label' => 'SUMMER20',         // shown to the user, e.g. the coupon code
+        'percent_off' => 20,           // or 'amount_off' => 1.50 (net, per period)
+        'duration' => 'repeating',     // once, repeating or forever
+        'duration_in_periods' => 3,    // only for repeating
+    ],
+]);
+
+$subscription->discount;               // {label, percent_off, amount_off, duration, duration_in_periods, periods_remaining}
+```
+
+A period is one unit of the subscription (a month for monthly prices). A free trial isn't a
+billed period: the discount starts with the first paid one. `periods_remaining` counts down with
+every billed period (null for `forever`, 0 once it ended); then `subscription.discount_ended`
+(`EventType::SUBSCRIPTION_DISCOUNT_ENDED`) is sent. A discount can't be combined with a
+`monthly_cap`. It is set when the subscription is created (app subscriptions and checkout
+sessions alike) and changed afterwards with
+[`change()`](#changing-running-subscriptions-trusted-apps). A resize (`predecessor_id`) doesn't
+carry it over: send the successor the rest (`'duration' => 'repeating'`,
+`'duration_in_periods' => $old->discount->periods_remaining`).
 
 ### Webhooks
 
@@ -436,6 +530,25 @@ arrive more than once or out of order: use `$event['id']` to skip duplicates, an
 object through the API when the current state matters. The admin panel can send a
 `webhook.test` event to check your endpoint.
 
+`subscription.renewed` (`EventType::SUBSCRIPTION_RENEWED`) is sent once for every period booked
+on the user's monthly order, **the first one included**, with `$event['data']['period']`:
+`{subscription_id, period_start, period_end, periods, first_period, unit, order_id, order_item_id,
+items, currency_iso, net_amount}` (`net_amount` after a discount). `first_period` is `true` for the
+subscription's first paid period (the checkout, sent after `subscription.activated`, or the first
+period after a free trial) and `false` for every later one (renewals, resuming an expired
+subscription, a unit change applied right away). Hourly subscriptions renew every hour, so this
+event is **opt-in**: select it explicitly for your endpoint, `*` doesn't include it.
+
+```php
+if ($event['type'] === EventType::SUBSCRIPTION_RENEWED) {
+    $period = $event['data']['period'];
+    // e.g. a commission per paid period; the first one may count differently
+    Commission::record($period['subscription_id'], $period['net_amount'], first: $period['first_period']);
+}
+```
+`order.*` events list the order's `items` and `invoice` like
+[app orders](#app-orders-trusted-apps-no-user-token).
+
 ### Errors
 
 Every failed request throws `Anikeen\Id\Exceptions\ApiException`, with the user's token as
@@ -566,7 +679,8 @@ try {
 Failures throw `Anikeen\Id\Exceptions\ApiException` with `status` (0 = not reachable), a stable
 `error` code (`already_active`, `already_cancelled`, `not_active`, `already_paused`,
 `already_resumed`, `billing_address_missing`, `not_changeable`, `subscription_not_found`,
-`idempotency_key_conflict`, `period_already_ended`, `elapsed_periods_not_allowed`,
+`idempotency_key_conflict`, `in_checkout_session`, `trial_already_used`, `proration_not_possible`,
+`credit_exceeds_bill`, `period_already_ended`, `elapsed_periods_not_allowed`,
 `elapsed_amount_exceeded`), the error response via `body()` and `isNotFound()`, `isConflict()`,
 `isTemporary()`:
 
@@ -584,6 +698,70 @@ try {
 }
 ```
 
+### Confirmable orders (trusted apps)
+
+Trusted apps can charge one-off orders right away (`'checkout' => true`). With `'confirm' => true`
+the user confirms and pays the order on Anikeen ID instead, like for a third-party app – e.g. a
+top-up the user starts in your app: Anikeen ID shows the order with VAT, the billing address and
+the payment method (one can be added there) and takes the payment.
+
+```php
+$order = app(AnikeenId::class)->createOrderForUser($team->owner->anikeen_id, [
+    'group' => $team->id,
+    'confirm' => true,
+    'return_url' => route('billing.topup.done'),   // same origin as one of your redirect URIs
+    'metadata' => ['topup' => $topup->id],          // returned as is, also in the order webhooks
+    'items' => [['type' => 'digital', 'name' => 'Credit', 'unit' => 'onetime', 'units' => 1, 'gross_price' => '10.00']],
+])->data;
+
+return redirect()->away($order->confirmation_url);
+// later: https://console.test/billing/topup/done?status=completed&order=01K…
+```
+
+`confirm` needs `items` and can't be combined with `checkout` or a `transaction` (422). The draft
+expires after 24 hours (`expires_at`): it is cancelled, `confirmation_url` becomes null and
+`checkout()` answers 409 `confirmation_expired`. Follow the order through its webhooks:
+`order.created`, then `order.completed` once paid (`order.payment_failed` for a declined charge)
+or `order.cancelled` when the user declines or it expires. `return_url` and `metadata` work for
+every order, also with the user's token (`$user->orders()->create([...])`).
+
+### Changing running subscriptions (trusted apps)
+
+`update()` changes a subscription before its checkout (afterwards only the description).
+`change()` changes price, unit, name, description or discount of a running subscription, like a
+plan change (send only what changes):
+
+```php
+use Anikeen\Id\Resources\AppSubscription;
+
+// upgrade now, prorated: the unused rest of the period is credited, the new price charged for it
+$subscription->change(['apply' => AppSubscription::APPLY_NOW, 'price' => '0.0274', 'name' => 'Cloud Server M']);
+
+// downgrade from the next period on
+$subscription->change(['apply' => AppSubscription::APPLY_PERIOD_END, 'price' => '4.99']);
+$subscription->scheduled_change;       // {applies_at, name, description, unit, price, discount, created_at}
+$subscription->cancelScheduledChange(); // keep the current values after all
+```
+
+- `now` credits the unused part of the current period at the rate it was billed at and charges
+  the rest at the new price, both on the user's open bill. A new `unit` starts a new, fully billed
+  period now. A downgrade whose credit would exceed the open bill is refused with 409
+  `credit_exceeds_bill`: schedule it for the period end instead. 409 `proration_not_possible` when
+  the current period wasn't billed to the subscription (e.g. a takeover); `period_end` works.
+- `period_end` changes nothing now; the next period is billed at the new values. A new
+  `period_end` change replaces the scheduled one, `now` drops it.
+- During a free trial nothing was billed: both just change what the trial ends in.
+- `discount` replaces the discount from the next billed period on, `null` ends it. When the unit
+  changes, a discount that counts in periods or an `amount_off` has to be sent again (422).
+- Subscriptions with a monthly cap change only with `period_end`.
+- Only running subscriptions can change: 409 `not_changeable` for drafts (use `update()`), paused,
+  cancelling, expired and cancelled ones.
+
+When a change takes effect (right away or at the period end), Anikeen ID sends
+`subscription.updated` (`EventType::SUBSCRIPTION_UPDATED`) with the old values of the changed
+fields in `$event['data']['previous_attributes']`. Telling the user about a price increase (and
+getting consent where needed) is up to your app.
+
 ### App orders (trusted apps, no user token)
 
 Orders that bill the app's subscriptions, read with the app's token (scope `orders:client`):
@@ -598,6 +776,67 @@ Each order has `status` (`processing` = current month, still collecting; `pendin
 paid; `completed`; `cancelled`), the totals, `payment_attempts`, `next_payment_attempt_at` (null =
 no more automatic retries) and `last_payment_error`.
 
+Collective (monthly) orders are kept **per app**: your subscriptions are never billed on the same
+order as another app's, even if both use the same `group` (or none); clients delegated to your app
+bill on your app's orders. `$order->oauth_client_id` is the app that bills the order.
+
+Orders also list their lines and their invoice, e.g. to show a team's invoices or to attribute
+amounts (commissions) per subscription:
+
+```php
+$order = app(AnikeenId::class)->appOrders()->find($orderId);
+
+foreach ($order->items as $item) {
+    $item->subscription_id;                     // null for lines that bill no subscription
+    $item->period_start; $item->period_end;     // ISO 8601, the end is exclusive; null without a period
+    $item->net_amount;                          // units × price, rounded to cents
+    $item->discount;                            // {label, percent_off, amount_off} on a discount line, else null
+}
+
+$order->invoice;                                // null until paid, then {id, number, status, …, pdf_url}
+$pdf = app(AnikeenId::class)->appOrders()->invoicePdf($orderId); // the invoice PDF (binary)
+```
+
+The net amount actually billed for a subscription is the sum of `net_amount` of its lines
+(discount lines are negative). `invoicePdf()` throws `ApiException` with 404 `invoice_not_found`
+before the order is paid and 409 `invoice_not_ready` while the PDF is still being rendered
+(usually seconds after the payment; try again later). Legacy orders from before collective orders
+were kept per app (`oauth_client_id` null) can also bill other apps' subscriptions: there `items`
+lists only your lines (the totals are the whole order's), `invoice->pdf_url` is null and
+`invoicePdf()` throws `ApiException` with 403 `invoice_includes_other_apps`.
+
+### Billing portal links (trusted apps)
+
+A "Manage billing" button for a user whose token your app doesn't have (e.g. the owner of a team
+your app bills): create a link to the user's billing pages on Anikeen ID with the app's token
+(scope `subscriptions:client` or `orders:client`). Like Stripe's customer portal, it works
+**without a login**:
+
+```php
+Route::post('teams/{team}/billing', function (Team $team) {
+    return redirect()->away($team->owner->appBillingPortalUrl([
+        'return_url' => route('teams.show', $team), // "Back to <app>"; same origin as one of your redirect URIs
+        'group' => $team->id,                       // only this group's subscriptions, orders and invoices
+        'flow' => 'invoices',                       // overview (default), payment_method, payment_method_update,
+                                                    // invoices, subscriptions or orders
+    ]));
+});
+
+app(AnikeenId::class)->createBillingPortalLinkForUser($userId, ['flow' => 'payment_method_update']);
+// {object: "billing_portal_link", url, user_id, flow, group, return_url, expires_at}
+```
+
+The link is **single use** and valid for about 15 minutes: create it when the user clicks and
+redirect right away; don't store, mail or reuse it (a second request with the same link, e.g. a
+reload, gets a 403). Opening it starts a portal session for that user that needs no login and
+signs nobody in: only the billing pages of the `flow`, only what bills your app's subscriptions
+(of the `group`), with "Back to *app*". The user's account settings, other apps and OAuth consent
+stay behind the normal login; signed in as another account, the portal still shows only the
+link's user. The session ends after an hour without activity or on "Back to *app*".
+`payment_method_update` leads straight to replacing the payment method (e.g. after a failed
+payment) and back to `return_url`. For the signed-in user with their own token,
+`$user->billingPortalUrl()` stays available.
+
 ### Checkout sessions (the user confirms several subscriptions at once)
 
 Instead of checking subscriptions out itself, an app can let the user confirm them on Anikeen ID,
@@ -874,6 +1113,7 @@ public function shippingPriceList(): Result
 ```php
 public function appOrders(): AppOrders
 public function appCheckoutSessions(): AppCheckoutSessions
+public function createBillingPortalLinkForUser(string $userId, array $attributes = []): object
 public function createOrderForUser(string $userId, array $attributes): Result
 public function createTransactionForUser(string $userId, array $attributes): Result
 ```
@@ -980,6 +1220,7 @@ public function appSubscriptions(): AppSubscriptions
 public function appCheckoutSessions(): AppCheckoutSessions
 public function checkoutSessions(): CheckoutSessions
 public function appOrders(): AppOrders
+public function appBillingPortalUrl(array $attributes = []): string
 public function setBillable(Billable|Model $billable): self
 public function getBillable(): Billable
 ```
diff --git a/README.stub b/README.stub
index e0efbcf..1bf43ae 100644
--- a/README.stub
+++ b/README.stub
@@ -382,8 +382,102 @@ same value as `status`):
 | `expired` | Paused and ran out; `resume()` starts a new period | no |
 | `cancelled` | Cancelled for good | no |
 
-There are shortcuts for each: `isDraft()`, `isPaused()`, `isCancelling()`, `isExpired()`,
-`isCancelled()`. App subscriptions (`appSubscriptions()`) have the same methods.
+There are shortcuts for each: `isDraft()`, `isTrial()`, `isPaused()`, `isCancelling()`,
+`isExpired()`, `isCancelled()`. App subscriptions (`appSubscriptions()`) have the same methods.
+
+#### Free trials
+
+Give a subscription a free trial with `trial_days` (1–365, counted from the user's confirmation or
+the checkout) or a fixed `trial_ends_at` (ISO 8601, in the future), not both. The subscription
+starts right away with `status` `trial` and nothing billed; the first period is billed when the
+trial ends. `trial_once` refuses the trial if the user already had one with your app in the same
+`group` (422 when creating, 409 `trial_already_used` when checking out):
+
+```php
+$subscription = $user->subscriptions()->create([
+    'name' => 'Pixel Stream Pass',
+    'unit' => 'month',
+    'price' => 6.714286,
+    'trial_days' => 14,
+    'trial_once' => true,
+]);
+```
+
+A few days before the trial ends, Anikeen ID sends `subscription.trial_will_end`
+(`EventType::SUBSCRIPTION_TRIAL_WILL_END`), e.g. to remind the user; `data.payment_method_missing`
+tells you whether the user still has to add a payment method. Cancelling during the trial
+bills nothing. Trials work the same for app subscriptions and per subscription of a checkout
+session.
+
+By default the user needs a payment method to confirm a trial. With `trial_payment_method`
+`TrialPaymentMethod::OPTIONAL` (only together with a trial; `TrialPaymentMethod::REQUIRED` is the
+default) the user can confirm it without one, as long as nothing else has to be paid: in a
+checkout session every subscription has to be such a trial. The confirmation page tells the user
+to add a payment method before the trial ends. If there is still none then, the subscription is
+**cancelled** at the trial's end instead of billed: `status` `cancelled`, `cancellation_reason`
+`CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD`, `subscription.cancelled` with
+`data.reason` set to the same value, and no `subscription.renewed`. Adding a payment method later
+doesn't bring it back – create a new subscription. The trial still counts for `trial_once`.
+Anikeen ID also mails the user a few days before such a trial ends without a payment method.
+
+```php
+use Anikeen\Id\Enums\CancellationReason;
+use Anikeen\Id\Enums\TrialPaymentMethod;
+use Anikeen\Id\Webhooks\EventType;
+
+$subscription = $user->appSubscriptions()->create([
+    'group' => $teamId,
+    'name' => 'Uptimr Pro',
+    'unit' => 'month',
+    'price' => 19.00,
+    'trial_days' => 14,
+    'trial_payment_method' => TrialPaymentMethod::OPTIONAL,
+]);
+
+// in your webhook handler
+$data = $event['data'];
+
+match ($event['type']) {
+    EventType::SUBSCRIPTION_TRIAL_WILL_END => $data['payment_method_missing']
+        ? Reminder::addPaymentMethod($data['object']['id'])
+        : null,
+    EventType::SUBSCRIPTION_CANCELLED => $data['reason'] === CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD
+        ? Pass::downgrade($data['object']['id'])
+        : Pass::revoke($data['object']['id']),
+    default => null,
+};
+```
+
+#### Discounts
+
+A `discount` (e.g. a coupon) lowers the price of billed periods: every discounted period gets a
+negative line with the `label` next to its usage on the same bill, until the discount ends.
+
+```php
+$subscription = $user->subscriptions()->create([
+    'name' => 'Pixel Stream Pass',
+    'unit' => 'month',
+    'price' => 6.714286,
+    'discount' => [
+        'label' => 'SUMMER20',         // shown to the user, e.g. the coupon code
+        'percent_off' => 20,           // or 'amount_off' => 1.50 (net, per period)
+        'duration' => 'repeating',     // once, repeating or forever
+        'duration_in_periods' => 3,    // only for repeating
+    ],
+]);
+
+$subscription->discount;               // {label, percent_off, amount_off, duration, duration_in_periods, periods_remaining}
+```
+
+A period is one unit of the subscription (a month for monthly prices). A free trial isn't a
+billed period: the discount starts with the first paid one. `periods_remaining` counts down with
+every billed period (null for `forever`, 0 once it ended); then `subscription.discount_ended`
+(`EventType::SUBSCRIPTION_DISCOUNT_ENDED`) is sent. A discount can't be combined with a
+`monthly_cap`. It is set when the subscription is created (app subscriptions and checkout
+sessions alike) and changed afterwards with
+[`change()`](#changing-running-subscriptions-trusted-apps). A resize (`predecessor_id`) doesn't
+carry it over: send the successor the rest (`'duration' => 'repeating'`,
+`'duration_in_periods' => $old->discount->periods_remaining`).
 
 ### Webhooks
 
@@ -436,6 +530,25 @@ arrive more than once or out of order: use `$event['id']` to skip duplicates, an
 object through the API when the current state matters. The admin panel can send a
 `webhook.test` event to check your endpoint.
 
+`subscription.renewed` (`EventType::SUBSCRIPTION_RENEWED`) is sent once for every period booked
+on the user's monthly order, **the first one included**, with `$event['data']['period']`:
+`{subscription_id, period_start, period_end, periods, first_period, unit, order_id, order_item_id,
+items, currency_iso, net_amount}` (`net_amount` after a discount). `first_period` is `true` for the
+subscription's first paid period (the checkout, sent after `subscription.activated`, or the first
+period after a free trial) and `false` for every later one (renewals, resuming an expired
+subscription, a unit change applied right away). Hourly subscriptions renew every hour, so this
+event is **opt-in**: select it explicitly for your endpoint, `*` doesn't include it.
+
+```php
+if ($event['type'] === EventType::SUBSCRIPTION_RENEWED) {
+    $period = $event['data']['period'];
+    // e.g. a commission per paid period; the first one may count differently
+    Commission::record($period['subscription_id'], $period['net_amount'], first: $period['first_period']);
+}
+```
+`order.*` events list the order's `items` and `invoice` like
+[app orders](#app-orders-trusted-apps-no-user-token).
+
 ### Errors
 
 Every failed request throws `Anikeen\Id\Exceptions\ApiException`, with the user's token as
@@ -566,7 +679,8 @@ try {
 Failures throw `Anikeen\Id\Exceptions\ApiException` with `status` (0 = not reachable), a stable
 `error` code (`already_active`, `already_cancelled`, `not_active`, `already_paused`,
 `already_resumed`, `billing_address_missing`, `not_changeable`, `subscription_not_found`,
-`idempotency_key_conflict`, `period_already_ended`, `elapsed_periods_not_allowed`,
+`idempotency_key_conflict`, `in_checkout_session`, `trial_already_used`, `proration_not_possible`,
+`credit_exceeds_bill`, `period_already_ended`, `elapsed_periods_not_allowed`,
 `elapsed_amount_exceeded`), the error response via `body()` and `isNotFound()`, `isConflict()`,
 `isTemporary()`:
 
@@ -584,6 +698,70 @@ try {
 }
 ```
 
+### Confirmable orders (trusted apps)
+
+Trusted apps can charge one-off orders right away (`'checkout' => true`). With `'confirm' => true`
+the user confirms and pays the order on Anikeen ID instead, like for a third-party app – e.g. a
+top-up the user starts in your app: Anikeen ID shows the order with VAT, the billing address and
+the payment method (one can be added there) and takes the payment.
+
+```php
+$order = app(AnikeenId::class)->createOrderForUser($team->owner->anikeen_id, [
+    'group' => $team->id,
+    'confirm' => true,
+    'return_url' => route('billing.topup.done'),   // same origin as one of your redirect URIs
+    'metadata' => ['topup' => $topup->id],          // returned as is, also in the order webhooks
+    'items' => [['type' => 'digital', 'name' => 'Credit', 'unit' => 'onetime', 'units' => 1, 'gross_price' => '10.00']],
+])->data;
+
+return redirect()->away($order->confirmation_url);
+// later: https://console.test/billing/topup/done?status=completed&order=01K…
+```
+
+`confirm` needs `items` and can't be combined with `checkout` or a `transaction` (422). The draft
+expires after 24 hours (`expires_at`): it is cancelled, `confirmation_url` becomes null and
+`checkout()` answers 409 `confirmation_expired`. Follow the order through its webhooks:
+`order.created`, then `order.completed` once paid (`order.payment_failed` for a declined charge)
+or `order.cancelled` when the user declines or it expires. `return_url` and `metadata` work for
+every order, also with the user's token (`$user->orders()->create([...])`).
+
+### Changing running subscriptions (trusted apps)
+
+`update()` changes a subscription before its checkout (afterwards only the description).
+`change()` changes price, unit, name, description or discount of a running subscription, like a
+plan change (send only what changes):
+
+```php
+use Anikeen\Id\Resources\AppSubscription;
+
+// upgrade now, prorated: the unused rest of the period is credited, the new price charged for it
+$subscription->change(['apply' => AppSubscription::APPLY_NOW, 'price' => '0.0274', 'name' => 'Cloud Server M']);
+
+// downgrade from the next period on
+$subscription->change(['apply' => AppSubscription::APPLY_PERIOD_END, 'price' => '4.99']);
+$subscription->scheduled_change;       // {applies_at, name, description, unit, price, discount, created_at}
+$subscription->cancelScheduledChange(); // keep the current values after all
+```
+
+- `now` credits the unused part of the current period at the rate it was billed at and charges
+  the rest at the new price, both on the user's open bill. A new `unit` starts a new, fully billed
+  period now. A downgrade whose credit would exceed the open bill is refused with 409
+  `credit_exceeds_bill`: schedule it for the period end instead. 409 `proration_not_possible` when
+  the current period wasn't billed to the subscription (e.g. a takeover); `period_end` works.
+- `period_end` changes nothing now; the next period is billed at the new values. A new
+  `period_end` change replaces the scheduled one, `now` drops it.
+- During a free trial nothing was billed: both just change what the trial ends in.
+- `discount` replaces the discount from the next billed period on, `null` ends it. When the unit
+  changes, a discount that counts in periods or an `amount_off` has to be sent again (422).
+- Subscriptions with a monthly cap change only with `period_end`.
+- Only running subscriptions can change: 409 `not_changeable` for drafts (use `update()`), paused,
+  cancelling, expired and cancelled ones.
+
+When a change takes effect (right away or at the period end), Anikeen ID sends
+`subscription.updated` (`EventType::SUBSCRIPTION_UPDATED`) with the old values of the changed
+fields in `$event['data']['previous_attributes']`. Telling the user about a price increase (and
+getting consent where needed) is up to your app.
+
 ### App orders (trusted apps, no user token)
 
 Orders that bill the app's subscriptions, read with the app's token (scope `orders:client`):
@@ -598,6 +776,67 @@ Each order has `status` (`processing` = current month, still collecting; `pendin
 paid; `completed`; `cancelled`), the totals, `payment_attempts`, `next_payment_attempt_at` (null =
 no more automatic retries) and `last_payment_error`.
 
+Collective (monthly) orders are kept **per app**: your subscriptions are never billed on the same
+order as another app's, even if both use the same `group` (or none); clients delegated to your app
+bill on your app's orders. `$order->oauth_client_id` is the app that bills the order.
+
+Orders also list their lines and their invoice, e.g. to show a team's invoices or to attribute
+amounts (commissions) per subscription:
+
+```php
+$order = app(AnikeenId::class)->appOrders()->find($orderId);
+
+foreach ($order->items as $item) {
+    $item->subscription_id;                     // null for lines that bill no subscription
+    $item->period_start; $item->period_end;     // ISO 8601, the end is exclusive; null without a period
+    $item->net_amount;                          // units × price, rounded to cents
+    $item->discount;                            // {label, percent_off, amount_off} on a discount line, else null
+}
+
+$order->invoice;                                // null until paid, then {id, number, status, …, pdf_url}
+$pdf = app(AnikeenId::class)->appOrders()->invoicePdf($orderId); // the invoice PDF (binary)
+```
+
+The net amount actually billed for a subscription is the sum of `net_amount` of its lines
+(discount lines are negative). `invoicePdf()` throws `ApiException` with 404 `invoice_not_found`
+before the order is paid and 409 `invoice_not_ready` while the PDF is still being rendered
+(usually seconds after the payment; try again later). Legacy orders from before collective orders
+were kept per app (`oauth_client_id` null) can also bill other apps' subscriptions: there `items`
+lists only your lines (the totals are the whole order's), `invoice->pdf_url` is null and
+`invoicePdf()` throws `ApiException` with 403 `invoice_includes_other_apps`.
+
+### Billing portal links (trusted apps)
+
+A "Manage billing" button for a user whose token your app doesn't have (e.g. the owner of a team
+your app bills): create a link to the user's billing pages on Anikeen ID with the app's token
+(scope `subscriptions:client` or `orders:client`). Like Stripe's customer portal, it works
+**without a login**:
+
+```php
+Route::post('teams/{team}/billing', function (Team $team) {
+    return redirect()->away($team->owner->appBillingPortalUrl([
+        'return_url' => route('teams.show', $team), // "Back to <app>"; same origin as one of your redirect URIs
+        'group' => $team->id,                       // only this group's subscriptions, orders and invoices
+        'flow' => 'invoices',                       // overview (default), payment_method, payment_method_update,
+                                                    // invoices, subscriptions or orders
+    ]));
+});
+
+app(AnikeenId::class)->createBillingPortalLinkForUser($userId, ['flow' => 'payment_method_update']);
+// {object: "billing_portal_link", url, user_id, flow, group, return_url, expires_at}
+```
+
+The link is **single use** and valid for about 15 minutes: create it when the user clicks and
+redirect right away; don't store, mail or reuse it (a second request with the same link, e.g. a
+reload, gets a 403). Opening it starts a portal session for that user that needs no login and
+signs nobody in: only the billing pages of the `flow`, only what bills your app's subscriptions
+(of the `group`), with "Back to *app*". The user's account settings, other apps and OAuth consent
+stay behind the normal login; signed in as another account, the portal still shows only the
+link's user. The session ends after an hour without activity or on "Back to *app*".
+`payment_method_update` leads straight to replacing the payment method (e.g. after a failed
+payment) and back to `return_url`. For the signed-in user with their own token,
+`$user->billingPortalUrl()` stays available.
+
 ### Checkout sessions (the user confirms several subscriptions at once)
 
 Instead of checking subscriptions out itself, an app can let the user confirm them on Anikeen ID,
diff --git a/src/Id/Concerns/HasSubscriptionStatus.php b/src/Id/Concerns/HasSubscriptionStatus.php
index 2cddb04..f69aa1e 100644
--- a/src/Id/Concerns/HasSubscriptionStatus.php
+++ b/src/Id/Concerns/HasSubscriptionStatus.php
@@ -48,6 +48,14 @@ trait HasSubscriptionStatus
         return in_array($this->status(), [SubscriptionStatus::TRIAL, SubscriptionStatus::ACTIVE, SubscriptionStatus::PAUSED, SubscriptionStatus::CANCELLING], true);
     }
 
+    /**
+     * In its free trial: running, nothing billed until trial_ends_at.
+     */
+    public function isTrial(): bool
+    {
+        return $this->status() === SubscriptionStatus::TRIAL;
+    }
+
     /**
      * Paused: runs until the paid period ends, then expires (resume() to continue).
      */
diff --git a/src/Id/Concerns/ManagesSubscriptions.php b/src/Id/Concerns/ManagesSubscriptions.php
index 33c78b4..6a6b302 100644
--- a/src/Id/Concerns/ManagesSubscriptions.php
+++ b/src/Id/Concerns/ManagesSubscriptions.php
@@ -2,6 +2,8 @@
 
 namespace Anikeen\Id\Concerns;
 
+use Anikeen\Id\AnikeenId;
+use Anikeen\Id\Exceptions\ApiException;
 use Anikeen\Id\Resources\AppCheckoutSessions;
 use Anikeen\Id\Resources\AppOrders;
 use Anikeen\Id\Resources\AppSubscriptions;
@@ -65,4 +67,20 @@ trait ManagesSubscriptions
     {
         return new AppOrders($this);
     }
+
+    /**
+     * A link to the user's billing pages on Anikeen ID that needs no login, created with the app's
+     * own token (trusted apps only, scope subscriptions:client or orders:client), e.g. for a
+     * "Manage billing" button; see AnikeenId::createBillingPortalLinkForUser() for the attributes
+     * (return_url, group, flow). Single use and valid for about 15 minutes: create it when the
+     * user clicks and redirect right away.
+     *
+     * @param array{return_url?: null|string, group?: null|string, flow?: null|string} $attributes
+     *
+     * @throws ApiException
+     */
+    public function appBillingPortalUrl(array $attributes = []): string
+    {
+        return app(AnikeenId::class)->createBillingPortalLinkForUser($this->appSubscriptions()->userId(), $attributes)->url;
+    }
 }
diff --git a/src/Id/Concerns/ManagesUserBilling.php b/src/Id/Concerns/ManagesUserBilling.php
index f5d91ad..8d9986e 100644
--- a/src/Id/Concerns/ManagesUserBilling.php
+++ b/src/Id/Concerns/ManagesUserBilling.php
@@ -2,9 +2,11 @@
 
 namespace Anikeen\Id\Concerns;
 
+use Anikeen\Id\Exceptions\ApiException;
 use Anikeen\Id\Resources\AppCheckoutSessions;
 use Anikeen\Id\Resources\AppOrders;
 use Anikeen\Id\Result;
+use Anikeen\Id\Support\AppRequest;
 use Throwable;
 
 /**
@@ -29,11 +31,48 @@ trait ManagesUserBilling
         return new AppCheckoutSessions();
     }
 
+    /**
+     * A link to a user's billing pages on Anikeen ID that needs no login, like Stripe's customer
+     * portal, e.g. for a "Manage billing" button of an app that bills another user's account (a
+     * team owner) without that user's token (trusted apps, scope subscriptions:client or
+     * orders:client). The link is single use and valid for about 15 minutes: create it when the
+     * user clicks and redirect right away, don't store it. It opens a portal session for that user
+     * only (no login, nobody signed in) with only the flow's billing pages and only what bills the
+     * app's subscriptions (of the group), leading back to return_url; it ends after an hour
+     * without activity.
+     *
+     * @param string $userId The user's Anikeen ID.
+     * @param array{
+     *     return_url?: null|string,
+     *     group?: null|string,
+     *     flow?: null|string
+     * } $attributes return_url: "Back to the app" (same origin as one of the app's redirect URIs,
+     *               422 otherwise).
+     *               group: only this group's subscriptions and the orders, invoices and
+     *               transactions billing them.
+     *               flow: overview (default), payment_method, payment_method_update (straight to
+     *               replacing the payment method, e.g. after a failed payment), invoices,
+     *               subscriptions or orders.
+     * @return object {object: "billing_portal_link", url, user_id, flow, group, return_url, expires_at}
+     *
+     * @throws ApiException 403 untrusted app or missing scope, 404 unknown user, 422 validation
+     */
+    public function createBillingPortalLinkForUser(string $userId, array $attributes = []): object
+    {
+        return AppRequest::send('POST', sprintf('v1/client/users/%s/billing-portal', $userId), $attributes)->data;
+    }
+
     /**
      * Create an order for a user (VAT from the billing address). With `checkout`, it is paid right
      * away: with the given `transaction` (a payment captured elsewhere) or by charging the user's
      * default payment method (402 when declined; the order stays pending and is retried).
      *
+     * With `confirm`, the user confirms and pays it on Anikeen ID instead (e.g. a top-up): the
+     * order stays a draft with `confirmation_url` (send the user there) and is cancelled if not
+     * confirmed within 24 hours (`expires_at`; afterwards checking it out answers 409
+     * "confirmation_expired"). Webhooks: order.created, order.completed once paid, or
+     * order.cancelled when the user declines or it expires.
+     *
      * @param string $userId The user's Anikeen ID.
      * @param array{
      *     group?: string,
@@ -43,11 +82,18 @@ trait ManagesUserBilling
      *     shipping_address?: array,
      *     items: array<array{type: string, name: string, description?: string, image_url?: string, price?: float|string, gross_price?: float|string, unit: string, units: int}>,
      *     checkout?: bool,
+     *     confirm?: bool,
+     *     return_url?: null|string,
+     *     metadata?: null|array,
      *     transaction_id?: string,
      *     transaction?: array,
      *     invoice_date?: string,
      *     currency_iso?: string
-     * } $attributes
+     * } $attributes confirm: needs items, can't be combined with checkout or a transaction.
+     *               return_url: where the user returns after confirming, with `status` and
+     *               `order` (same origin as one of the app's redirect URIs, 422 otherwise).
+     *               metadata: the app's own data (max. 50 keys), returned as is in the API and
+     *               the order webhooks.
      * @throws Throwable
      */
     public function createOrderForUser(string $userId, array $attributes): Result
diff --git a/src/Id/Enums/CancellationReason.php b/src/Id/Enums/CancellationReason.php
new file mode 100644
index 0000000..94ff94a
--- /dev/null
+++ b/src/Id/Enums/CancellationReason.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace Anikeen\Id\Enums;
+
+/**
+ * `cancellation_reason` of a subscription (and `data.reason` of `subscription.cancelled`): why
+ * Anikeen ID's billing ended it. Null when the user, the app or an admin cancelled it.
+ */
+class CancellationReason
+{
+    /** Its free trial (`trial_payment_method` optional) ended without a payment method: cancelled at the trial's end, nothing billed. */
+    const TRIAL_ENDED_WITHOUT_PAYMENT_METHOD = 'trial_ended_without_payment_method';
+}
diff --git a/src/Id/Enums/TrialPaymentMethod.php b/src/Id/Enums/TrialPaymentMethod.php
new file mode 100644
index 0000000..3abda33
--- /dev/null
+++ b/src/Id/Enums/TrialPaymentMethod.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Anikeen\Id\Enums;
+
+/**
+ * `trial_payment_method` of a subscription with a free trial: whether the user needs a payment
+ * method to confirm it. Null on subscriptions without a trial.
+ */
+class TrialPaymentMethod
+{
+    /** A payment method is needed to confirm the trial (the default). */
+    const REQUIRED = 'required';
+
+    /**
+     * The trial can be confirmed without a payment method (if nothing else has to be paid). If the
+     * user still has none when the trial ends, the subscription is cancelled then instead of billed
+     * (`cancellation_reason` CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD).
+     */
+    const OPTIONAL = 'optional';
+}
diff --git a/src/Id/Resources/AppCheckoutSessions.php b/src/Id/Resources/AppCheckoutSessions.php
index 5c479f4..16eb8a9 100644
--- a/src/Id/Resources/AppCheckoutSessions.php
+++ b/src/Id/Resources/AppCheckoutSessions.php
@@ -36,7 +36,12 @@ class AppCheckoutSessions
      *         predecessor_id?: null|string,
      *         vat_rate?: float,
      *         payload?: null|array,
-     *         ends_at?: null|string
+     *         ends_at?: null|string,
+     *         trial_days?: null|int,
+     *         trial_ends_at?: null|string,
+     *         trial_once?: bool,
+     *         trial_payment_method?: null|string,
+     *         discount?: null|array{label: string, percent_off?: float|string, amount_off?: float|string, duration: string, duration_in_periods?: int}
      *     }>,
      *     return_url?: null|string,
      *     metadata?: null|array,
@@ -45,6 +50,11 @@ class AppCheckoutSessions
      * } $attributes return_url must share scheme, host and port with one of the app's redirect
      *               URIs; the user comes back to it with `status` and `checkout_session`. A
      *               repeated idempotency_key returns the first session instead of a new one.
+     *               trial_days / trial_ends_at give a subscription a free trial from the user's
+     *               confirmation on; trial_once is allowed on one subscription per group.
+     *               trial_payment_method `optional`: the session can be confirmed without a
+     *               payment method only if all of its subscriptions are such trials.
+     *               discount: see AppSubscriptions::create(); the confirmation page shows it.
      *
      * @throws ApiException 422 validation (e.g. return_url), 409 "idempotency_key_conflict"
      */
diff --git a/src/Id/Resources/AppOrders.php b/src/Id/Resources/AppOrders.php
index 0457e2c..41750bb 100644
--- a/src/Id/Resources/AppOrders.php
+++ b/src/Id/Resources/AppOrders.php
@@ -13,9 +13,22 @@ use Illuminate\Database\Eloquent\Model;
  * scope orders:client) - of one user ($user->appOrders()) or of all users
  * (app(AnikeenId::class)->appOrders()). Nothing is requested until a method is called.
  *
- * Each order is an object with id, user_id, group, status (processing|pending|completed|cancelled),
- * is_collective, net_total, vat_total, gross_total, currency_iso, created_at, paid_at,
- * payment_attempts, next_payment_attempt_at and last_payment_error ({code, message} or null).
+ * Each order is an object with id, user_id, oauth_client_id (the app that bills it: collective
+ * orders are kept per app, even for the same group; null on legacy orders that billed several
+ * apps), group, metadata, status (processing|pending|completed|cancelled), is_collective,
+ * net_total, vat_total, gross_total, currency_iso, created_at, paid_at, payment_attempts,
+ * next_payment_attempt_at, last_payment_error ({code, message} or null), and
+ *
+ * - items: the order's lines of the app's subscriptions (all lines, except on legacy orders that
+ *   also billed other apps), each {id, name, description, type, image_url, units, unit,
+ *   price, vat_rate, subscription_id, meter, monthly_cap, discount, period_start, period_end,
+ *   net_amount, vat_amount, gross_amount}. period_end is exclusive (the start of the next
+ *   period); both are null for lines without a period. discount ({label, percent_off,
+ *   amount_off}) marks the negative line of a subscription's discount, else null. The net amount
+ *   a subscription was billed is the sum of net_amount of its lines.
+ * - invoice: null until the order is paid, then {id, number, type, status (pending while the PDF
+ *   is being rendered, then completed), service_period_from, service_period_to, created_at,
+ *   pdf_url}; see invoicePdf().
  */
 class AppOrders
 {
@@ -81,6 +94,22 @@ class AppOrders
         return !$this->billable || $order->user_id === $this->userId() ? $order : null;
     }
 
+    /**
+     * The PDF of an order's invoice (binary string, with the embedded e-invoice), the same as its
+     * `invoice.pdf_url` with the app's token.
+     *
+     * @throws ApiException 404 "order_not_found", 404 "invoice_not_found" (not paid yet),
+     *                      409 "invoice_not_ready" (still being rendered, try again later)
+     */
+    public function invoicePdf(string $orderId): string
+    {
+        if ($this->billable && !$this->find($orderId)) {
+            throw new ApiException('Order not found.', 404, 'order_not_found');
+        }
+
+        return (string) AppRequest::send('GET', sprintf('v1/client/orders/%s/invoice', $orderId))->response()?->getBody();
+    }
+
     private function userId(): string
     {
         return (new AppSubscriptions($this->billable))->userId();
diff --git a/src/Id/Resources/AppSubscription.php b/src/Id/Resources/AppSubscription.php
index f4f58aa..0016f90 100644
--- a/src/Id/Resources/AppSubscription.php
+++ b/src/Id/Resources/AppSubscription.php
@@ -29,6 +29,9 @@ use JsonSerializable;
  * @property ?string $status draft, trial, active, paused, cancelling, expired or cancelled, see status()
  * @property ?string $cancels_at when a scheduled cancellation takes effect
  * @property ?string $trial_ends_at
+ * @property ?string $trial_payment_method required or optional with a trial (TrialPaymentMethod), null without
+ * @property ?string $cancellation_reason why the billing cancelled it (CancellationReason), null otherwise
+ * @property ?object $discount {label, percent_off, amount_off, duration, duration_in_periods, periods_remaining}; periods_remaining is null for `forever`, 0 once it ended
  * @property ?string $starts_at
  * @property ?string $ends_at
  * @property ?string $accounting_at
@@ -37,11 +40,18 @@ use JsonSerializable;
  * @property ?array $payload
  * @property ?string $idempotency_key
  * @property ?string $checkout_session_id the checkout session the user confirms it in, if any
+ * @property ?object $scheduled_change {applies_at, name, description, unit, price, discount, created_at}: a change() for the period end
  */
 class AppSubscription implements JsonSerializable
 {
     use HasSubscriptionStatus;
 
+    /** change(): prorated, right away. */
+    public const APPLY_NOW = 'now';
+
+    /** change(): from the next period on (scheduled_change until then). */
+    public const APPLY_PERIOD_END = 'period_end';
+
     public function __construct(protected object $data)
     {
     }
@@ -60,6 +70,7 @@ class AppSubscription implements JsonSerializable
      * Change a subscription (send only what changes). Before checkout everything can change;
      * afterwards only the description, which names what the customer pays for and is shown
      * on their bills, e.g. `$subscription->update(['description' => 'web-01.example.com'])`.
+     * Prices of running subscriptions change with change().
      *
      * @throws ApiException
      */
@@ -68,6 +79,51 @@ class AppSubscription implements JsonSerializable
         return $this->send('PUT', '', $attributes);
     }
 
+    /**
+     * Change a running subscription (send only what changes), like a plan change:
+     *
+     * - `apply: now`: prorated – the unused rest of the current period is credited at the rate it
+     *   was billed at and charged at the new price on the user's open bill. A new unit starts a
+     *   new, fully billed period now. A downgrade whose credit exceeds the open bill is refused
+     *   (409 "credit_exceeds_bill"): schedule it for the period end instead.
+     * - `apply: period_end`: nothing changes now; the subscription has `scheduled_change` and the
+     *   next period is billed at the new values. A new scheduled change replaces the previous one.
+     *
+     * During a free trial nothing was billed, so both just change what the trial ends in.
+     * Webhook `subscription.updated` (with `data.previous_attributes`) when the change takes effect.
+     *
+     * @param array{
+     *     apply: string,
+     *     price?: float|string,
+     *     unit?: string,
+     *     name?: string,
+     *     description?: null|string,
+     *     discount?: null|array{label: string, percent_off?: float|string, amount_off?: float|string, duration: string, duration_in_periods?: int}
+     * } $attributes apply: self::APPLY_NOW or self::APPLY_PERIOD_END.
+     *               unit: a recurring unit (hour, day, week, month, year).
+     *               discount: replaces the discount from the next billed period on, null ends it;
+     *               required with a new unit when the current one counts in periods or is an
+     *               amount_off. Subscriptions with a monthly cap change only at the period end.
+     *
+     * @throws ApiException 409 "not_changeable" (not running: draft, paused, cancelling, …),
+     *                      "proration_not_possible", "credit_exceeds_bill",
+     *                      "billing_address_missing"; 422 validation
+     */
+    public function change(array $attributes): self
+    {
+        return $this->send('PUT', '/change', $attributes);
+    }
+
+    /**
+     * Drop the change scheduled for the period end (nothing happens without one).
+     *
+     * @throws ApiException
+     */
+    public function cancelScheduledChange(): self
+    {
+        return $this->send('DELETE', '/change');
+    }
+
     /**
      * Activate the subscription and bill its first period.
      *
diff --git a/src/Id/Resources/AppSubscriptions.php b/src/Id/Resources/AppSubscriptions.php
index 777da58..433f6c2 100644
--- a/src/Id/Resources/AppSubscriptions.php
+++ b/src/Id/Resources/AppSubscriptions.php
@@ -49,6 +49,11 @@ class AppSubscriptions
      *     vat_rate?: float,
      *     payload?: null|array,
      *     ends_at?: null|string,
+     *     trial_days?: null|int,
+     *     trial_ends_at?: null|string,
+     *     trial_once?: bool,
+     *     trial_payment_method?: null|string,
+     *     discount?: null|array{label: string, percent_off?: float|string, amount_off?: float|string, duration: string, duration_in_periods?: int},
      *     idempotency_key?: null|string
      * } $attributes With an idempotency_key (max. 191 characters), a retried call returns the
      *               subscription created by the first one instead of a duplicate.
@@ -56,8 +61,21 @@ class AppSubscriptions
      *               at most 2 decimals, not below price; null = no cap).
      *               predecessor_id: the subscription this one replaces (a resize; same user and
      *               app, checked out, not cancelled): both share the monthly cap within a month.
+     *               trial_days: a free trial of 1–365 days from the checkout on (status `trial`,
+     *               nothing billed; the first period is billed when it ends), or
+     *               trial_ends_at: a fixed end of the trial (ISO 8601, in the future), not both.
+     *               trial_once: refuse the trial if the user already had one with the app in the
+     *               same group (422 here, 409 "trial_already_used" on checkout).
+     *               trial_payment_method: TrialPaymentMethod::REQUIRED (default) or ::OPTIONAL,
+     *               only with a trial: with `optional` the user may confirm it without a payment
+     *               method, and without one at the trial's end it is cancelled instead of billed.
+     *               discount: e.g. a coupon, as a negative line next to each billed period:
+     *               label (shown to the user, max. 100 characters), percent_off (0.01–100) or
+     *               amount_off (net per period, at most the price), duration `once` (the first
+     *               billed period), `repeating` (duration_in_periods billed periods) or
+     *               `forever`. Not combinable with a monthly_cap.
      *
-     * @throws ApiException
+     * @throws ApiException 422 validation, 409 "idempotency_key_conflict", …
      */
     public function create(array $attributes): AppSubscription
     {
diff --git a/src/Id/Resources/Order.php b/src/Id/Resources/Order.php
index 8ecd5f3..6996874 100644
--- a/src/Id/Resources/Order.php
+++ b/src/Id/Resources/Order.php
@@ -8,7 +8,14 @@ use Throwable;
 
 /**
  * @property string $id
- * @property null|string $confirmation_url where the user confirms it (third-party apps)
+ * @property null|string $confirmation_url where the user confirms it (third-party apps, or `confirm`)
+ * @property null|string $oauth_client_id the app that bills the order: the app that created it, or for a monthly
+ *                                        (collective) order the app whose subscriptions it bills; collective orders
+ *                                        are kept per app. null for Anikeen's own (and legacy orders of several apps)
+ * @property null|string $group
+ * @property null|object $metadata the app's own data, returned as is
+ * @property null|string $return_url where the user returns after confirming
+ * @property null|string $expires_at when a draft created with `confirm` is cancelled unless confirmed
  */
 class Order extends BaseResource
 {
@@ -53,10 +60,14 @@ class Order extends BaseResource
      *           country_iso: string,
      *           phone_number: null|string,
      *           email: null|string
-     *      }
+     *      },
+     *      group?: null|string,
+     *      metadata?: null|array
      *  } $attributes The order data:
      *    - billing_address:  Billing address (ISO 3166-1 alpha-2 country code)
      *    - shipping_address: Shipping address for physical items (first name, last name, address, postal code, city, ISO 3166-1 alpha-2 country code)
+     *    - group:            The app's group (optional)
+     *    - metadata:         The app's own data (max. 50 keys), only while the order is a draft (optional)
      * @throws Throwable
      */
     public function update(array $attributes = []): self
@@ -69,6 +80,8 @@ class Order extends BaseResource
     /**
      * Checkout given order from the current user.
      *
+     * A draft created with `confirm` can't be checked out once it expired (409 "confirmation_expired").
+     *
      * @throws Throwable
      */
     public function checkout(): self
diff --git a/src/Id/Resources/Orders.php b/src/Id/Resources/Orders.php
index e56a21f..6c6b62d 100644
--- a/src/Id/Resources/Orders.php
+++ b/src/Id/Resources/Orders.php
@@ -48,6 +48,10 @@ class Orders extends BaseCollection
      *          phone_number: null|string,
      *          email: null|string
      *     },
+     *     group?: null|string,
+     *     confirm?: bool,
+     *     return_url?: null|string,
+     *     metadata?: null|array,
      *     items: array<array{
      *         type:         string,
      *         name:         string,
@@ -61,6 +65,10 @@ class Orders extends BaseCollection
      * } $attributes The order data:
      *   - billing_address:  Billing address (ISO 3166-1 alpha-2 country code)
      *   - shipping_address: Shipping address for physical items (first name, last name, address, postal code, city, ISO 3166-1 alpha-2 country code)
+     *   - group:            The app's group, e.g. a team (optional)
+     *   - confirm:          Trusted apps: leave confirming and paying to the user (confirmation_url, expires after 24 hours; optional)
+     *   - return_url:       Where the user returns after confirming (same origin as one of the app's redirect URIs; optional)
+     *   - metadata:         The app's own data (max. 50 keys), returned as is in the API and webhooks (optional)
      *   - items:            Array of order items:
      *       - type:        digital, physical or physical-reduced (VAT category)
      *       - price/gross_price: net or gross unit price, one of both
diff --git a/src/Id/Resources/Subscription.php b/src/Id/Resources/Subscription.php
index b26e2c2..b4b4245 100644
--- a/src/Id/Resources/Subscription.php
+++ b/src/Id/Resources/Subscription.php
@@ -27,6 +27,9 @@ use Throwable;
  * @property string $ends_at
  * @property ?string $cancels_at when a scheduled cancellation takes effect
  * @property ?string $trial_ends_at
+ * @property ?string $trial_payment_method required or optional with a trial (TrialPaymentMethod), null without
+ * @property ?string $cancellation_reason why the billing cancelled it (CancellationReason), null otherwise
+ * @property ?object $discount {label, percent_off, amount_off, duration, duration_in_periods, periods_remaining}; periods_remaining is null for `forever`, 0 once it ended
  * @property null|string $confirmation_url where the user confirms it (third-party apps)
  */
 class Subscription extends BaseResource
diff --git a/src/Id/Resources/Subscriptions.php b/src/Id/Resources/Subscriptions.php
index 9b2a0f9..a7d569e 100644
--- a/src/Id/Resources/Subscriptions.php
+++ b/src/Id/Resources/Subscriptions.php
@@ -24,7 +24,12 @@ class Subscriptions extends BaseCollection
      *      predecessor_id?: null|string,
      *      vat_rate: float,
      *      payload: null|array,
-     *      ends_at: null|string
+     *      ends_at: null|string,
+     *      trial_days?: null|int,
+     *      trial_ends_at?: null|string,
+     *      trial_once?: bool,
+     *      trial_payment_method?: null|string,
+     *      discount?: null|array{label: string, percent_off?: float|string, amount_off?: float|string, duration: string, duration_in_periods?: int}
      *  } $attributes The subscription data:
      *    - group:          The group (optional)
      *    - name:           The name
@@ -36,6 +41,11 @@ class Subscriptions extends BaseCollection
      *    - vat_rate:       The VAT rate (required when set)
      *    - payload:        The payload (optional)
      *    - ends_at:        The end date (optional)
+     *    - trial_days:     A free trial of 1–365 days from the user's confirmation on (optional)
+     *    - trial_ends_at:  Or a fixed end of the free trial (ISO 8601, in the future; optional)
+     *    - trial_once:     Refuse the trial if the user already had one with the app in the group (optional)
+     *    - trial_payment_method: TrialPaymentMethod::REQUIRED (default) or ::OPTIONAL, only with a trial (optional)
+     *    - discount:       A discount per billed period, see AppSubscriptions::create() (optional)
      * @throws Throwable
      */
     public function create(array $attributes): Subscription
diff --git a/src/Id/Webhooks/EventType.php b/src/Id/Webhooks/EventType.php
index e4b8b44..06d5f21 100644
--- a/src/Id/Webhooks/EventType.php
+++ b/src/Id/Webhooks/EventType.php
@@ -18,9 +18,34 @@ final class EventType
     public const SUBSCRIPTION_ACTIVATED = 'subscription.activated';
     public const SUBSCRIPTION_PAUSED = 'subscription.paused';
     public const SUBSCRIPTION_RESUMED = 'subscription.resumed';
+    /** `data.reason`: why the billing cancelled it (CancellationReason, e.g. a trial that ended without a payment method), else null. */
     public const SUBSCRIPTION_CANCELLED = 'subscription.cancelled';
     public const SUBSCRIPTION_EXPIRED = 'subscription.expired';
 
+    /**
+     * The free trial of a running subscription ends in a few days (see trial_ends_at); billing
+     * starts then. `data.payment_method_missing`: the user has no payment method yet (with
+     * trial_payment_method `optional` the subscription then ends with the trial).
+     */
+    public const SUBSCRIPTION_TRIAL_WILL_END = 'subscription.trial_will_end';
+
+    /** The last discounted period of a subscription was billed; the following ones are billed at the full price. */
+    public const SUBSCRIPTION_DISCOUNT_ENDED = 'subscription.discount_ended';
+
+    /**
+     * The price, unit, name, description or discount of a running subscription changed (right away
+     * or at the period end); `data.previous_attributes` has the changed fields' old values.
+     */
+    public const SUBSCRIPTION_UPDATED = 'subscription.updated';
+
+    /**
+     * A period of a subscription was booked on its collective order, the first one included;
+     * `data.period` describes it, `data.period.first_period` is true for the subscription's first
+     * paid period (checkout or the end of a free trial). Opt-in: only endpoints that select this
+     * event get it (not through `*`).
+     */
+    public const SUBSCRIPTION_RENEWED = 'subscription.renewed';
+
     /** The user confirmed a checkout session: all of its subscriptions are running (sent after their subscription.activated). */
     public const CHECKOUT_COMPLETED = 'checkout.completed';
 
diff --git a/tests/Id/AppOrdersTest.php b/tests/Id/AppOrdersTest.php
index 9bcb0a0..e88e600 100644
--- a/tests/Id/AppOrdersTest.php
+++ b/tests/Id/AppOrdersTest.php
@@ -4,6 +4,8 @@ namespace Anikeen\Id\Tests;
 
 use Anikeen\Id\AnikeenId;
 use Anikeen\Id\Billable;
+use Anikeen\Id\Exceptions\ApiException;
+use GuzzleHttp\Psr7\Response;
 use Illuminate\Database\Eloquent\Model;
 
 class AppOrdersTest extends TestCase
@@ -68,4 +70,65 @@ class AppOrdersTest extends TestCase
         $this->assertNull($orders->find('o1'));
         $this->assertSame('o1', $orders->find('o1')->id);
     }
+
+    public function test_orders_list_their_lines_and_invoice(): void
+    {
+        $this->respond(200, ['data' => [
+            'id' => 'o1',
+            'user_id' => '01JUSER',
+            'group' => 'team-1',
+            'metadata' => ['topup' => '7'],
+            'items' => [
+                ['id' => 'i1', 'subscription_id' => '01JSUB', 'units' => 1, 'price' => 10, 'period_start' => '2026-11-01T00:00:00+00:00', 'period_end' => '2026-12-01T00:00:00+00:00', 'net_amount' => 10, 'discount' => null],
+                ['id' => 'i2', 'subscription_id' => '01JSUB', 'units' => 1, 'price' => -2, 'period_start' => '2026-11-01T00:00:00+00:00', 'period_end' => '2026-12-01T00:00:00+00:00', 'net_amount' => -2, 'discount' => ['label' => 'SUMMER20', 'percent_off' => 20, 'amount_off' => null]],
+            ],
+            'invoice' => ['id' => 'inv1', 'number' => 'RE-2026-0001', 'status' => 'completed', 'pdf_url' => 'https://id.test/api/v1/client/orders/o1/invoice'],
+        ]]);
+
+        $order = $this->owner()->appOrders()->find('o1');
+
+        $this->assertSame('7', $order->metadata->topup);
+        $this->assertSame(8, array_sum(array_map(fn ($item) => $item->net_amount, array_filter($order->items, fn ($item) => $item->subscription_id === '01JSUB'))));
+        $this->assertSame('SUMMER20', $order->items[1]->discount->label);
+        $this->assertSame('RE-2026-0001', $order->invoice->number);
+    }
+
+    public function test_the_invoice_pdf_is_downloaded_with_the_app_token(): void
+    {
+        $this->http->append(new Response(200, ['Content-Type' => 'application/pdf'], '%PDF-1.7 invoice'));
+        $this->respond(200, ['data' => ['id' => 'o1', 'user_id' => '01JUSER']]);
+        $this->http->append(new Response(200, ['Content-Type' => 'application/pdf'], '%PDF-1.7 invoice'));
+
+        $this->assertSame('%PDF-1.7 invoice', app(AnikeenId::class)->appOrders()->invoicePdf('o1'));
+        $this->assertSame('%PDF-1.7 invoice', $this->owner()->appOrders()->invoicePdf('o1'));
+
+        $calls = array_map(fn ($entry) => $entry['request']->getMethod() . ' ' . $entry['request']->getUri()->getPath() . ' ' . $entry['request']->getHeaderLine('Authorization'), $this->sent);
+        $this->assertSame([
+            'GET /api/v1/client/orders/o1/invoice Bearer app-token',
+            'GET /api/v1/client/orders/o1 Bearer app-token',
+            'GET /api/v1/client/orders/o1/invoice Bearer app-token',
+        ], $calls);
+    }
+
+    public function test_an_invoice_that_is_not_ready_is_a_conflict(): void
+    {
+        $this->respond(409, ['message' => 'The invoice document is still being created.', 'error' => 'invoice_not_ready']);
+        $this->respond(200, ['data' => ['id' => 'o1', 'user_id' => 'someone-else']]);
+
+        try {
+            app(AnikeenId::class)->appOrders()->invoicePdf('o1');
+            $this->fail('Expected an ApiException.');
+        } catch (ApiException $e) {
+            $this->assertTrue($e->isConflict());
+            $this->assertSame('invoice_not_ready', $e->error);
+        }
+
+        try {
+            $this->owner()->appOrders()->invoicePdf('o1');
+            $this->fail('Expected an ApiException.');
+        } catch (ApiException $e) {
+            $this->assertTrue($e->isNotFound());
+            $this->assertSame('order_not_found', $e->error);
+        }
+    }
 }
diff --git a/tests/Id/AppSubscriptionsTest.php b/tests/Id/AppSubscriptionsTest.php
index 8003bc9..46947b2 100644
--- a/tests/Id/AppSubscriptionsTest.php
+++ b/tests/Id/AppSubscriptionsTest.php
@@ -4,7 +4,10 @@ namespace Anikeen\Id\Tests;
 
 use Anikeen\Id\AnikeenId;
 use Anikeen\Id\Billable;
+use Anikeen\Id\Enums\CancellationReason;
+use Anikeen\Id\Enums\TrialPaymentMethod;
 use Anikeen\Id\Exceptions\ApiException;
+use Anikeen\Id\Resources\AppSubscription;
 use GuzzleHttp\Exception\ConnectException;
 use GuzzleHttp\Psr7\Request;
 use Illuminate\Database\Eloquent\Model;
@@ -255,6 +258,99 @@ class AppSubscriptionsTest extends TestCase
         }
     }
 
+    public function test_a_subscription_starts_with_a_free_trial(): void
+    {
+        $this->respond(201, $this->subscription());
+        $this->respond(200, $this->subscription(['active' => true, 'autorenew' => true, 'status' => 'trial', 'starts_at' => '2026-11-04T10:00:00+00:00', 'trial_ends_at' => date(DATE_ATOM, time() + 14 * 86400)]));
+
+        $subscription = $this->owner()->appSubscriptions()->create(['group' => 'team-1', 'name' => 'Pro', 'unit' => 'month', 'price' => '9.99', 'trial_days' => 14, 'trial_once' => true]);
+        $subscription->checkout();
+
+        $this->assertSame(['group' => 'team-1', 'name' => 'Pro', 'unit' => 'month', 'price' => '9.99', 'trial_days' => 14, 'trial_once' => true, 'user_id' => '01JUSER'], $this->sentJson(0));
+        $this->assertTrue($subscription->isTrial());
+        $this->assertTrue($subscription->isActive());
+    }
+
+    public function test_a_trial_can_be_confirmed_without_a_payment_method_and_end_cancelled(): void
+    {
+        $this->respond(201, $this->subscription(['trial_days' => 14, 'trial_payment_method' => 'optional']));
+        $this->respond(200, $this->subscription(['active' => false, 'cancelled' => true, 'status' => 'cancelled', 'starts_at' => '2026-11-04T10:00:00+00:00', 'trial_ends_at' => '2026-11-18T10:00:00+00:00', 'cancels_at' => '2026-11-18T10:00:00+00:00', 'trial_payment_method' => 'optional', 'cancellation_reason' => 'trial_ended_without_payment_method']));
+
+        $subscription = $this->owner()->appSubscriptions()->create(['name' => 'Pro', 'unit' => 'month', 'price' => '9.99', 'trial_days' => 14, 'trial_payment_method' => TrialPaymentMethod::OPTIONAL]);
+
+        $this->assertSame('optional', $this->sentJson(0)['trial_payment_method']);
+        $this->assertSame(TrialPaymentMethod::OPTIONAL, $subscription->trial_payment_method);
+
+        $ended = $this->owner()->appSubscriptions()->find('01JSUB');
+        $this->assertTrue($ended->isCancelled());
+        $this->assertSame(CancellationReason::TRIAL_ENDED_WITHOUT_PAYMENT_METHOD, $ended->cancellation_reason);
+    }
+
+    public function test_a_used_trial_is_refused_on_checkout(): void
+    {
+        $this->respond(201, $this->subscription());
+        $this->respond(409, ['message' => 'The user already had a free trial.', 'error' => 'trial_already_used']);
+
+        $subscription = $this->owner()->appSubscriptions()->create(['name' => 'Pro', 'unit' => 'month', 'price' => '9.99', 'trial_ends_at' => '2026-12-01T00:00:00+01:00', 'trial_once' => true]);
+
+        try {
+            $subscription->checkout();
+            $this->fail('Expected an ApiException.');
+        } catch (ApiException $e) {
+            $this->assertTrue($e->isConflict());
+            $this->assertSame('trial_already_used', $e->error);
+        }
+    }
+
+    public function test_a_subscription_is_created_with_a_discount(): void
+    {
+        $discount = ['label' => 'SUMMER20', 'percent_off' => 20, 'duration' => 'repeating', 'duration_in_periods' => 3];
+        $this->respond(201, $this->subscription(['discount' => [...$discount, 'amount_off' => null, 'periods_remaining' => 3]]));
+
+        $subscription = $this->owner()->appSubscriptions()->create(['name' => 'Pro', 'unit' => 'month', 'price' => '9.99', 'discount' => $discount]);
+
+        $this->assertSame($discount, $this->sentJson(0)['discount']);
+        $this->assertSame('SUMMER20', $subscription->discount->label);
+        $this->assertSame(3, $subscription->discount->periods_remaining);
+    }
+
+    public function test_a_running_subscription_is_changed_now_or_at_the_period_end(): void
+    {
+        $change = ['applies_at' => '2026-12-01T00:00:00+00:00', 'name' => 'Pro', 'description' => null, 'unit' => 'month', 'price' => 14.99, 'discount' => null, 'created_at' => '2026-11-04T10:00:00+00:00'];
+        $this->respond(200, $this->subscription(['active' => true, 'price' => 14.99]));
+        $this->respond(200, $this->subscription(['active' => true, 'price' => 14.99, 'scheduled_change' => $change]));
+        $this->respond(200, $this->subscription(['active' => true, 'price' => 14.99, 'scheduled_change' => null]));
+
+        $subscription = new AppSubscription((object) $this->subscription(['active' => true])['data']);
+
+        $this->assertSame(14.99, $subscription->change(['apply' => AppSubscription::APPLY_NOW, 'price' => '14.99', 'discount' => null])->price);
+        $this->assertSame('2026-12-01T00:00:00+00:00', $subscription->change(['apply' => AppSubscription::APPLY_PERIOD_END, 'unit' => 'month', 'name' => 'Pro'])->scheduled_change->applies_at);
+        $this->assertNull($subscription->cancelScheduledChange()->scheduled_change);
+
+        $this->assertSame([
+            'PUT /api/v1/client/subscriptions/01JSUB/change Bearer app-token',
+            'PUT /api/v1/client/subscriptions/01JSUB/change Bearer app-token',
+            'DELETE /api/v1/client/subscriptions/01JSUB/change Bearer app-token',
+        ], array_map(fn ($entry) => $entry['request']->getMethod() . ' ' . $entry['request']->getUri()->getPath() . ' ' . $entry['request']->getHeaderLine('Authorization'), $this->sent));
+        $this->assertSame(['apply' => 'now', 'price' => '14.99', 'discount' => null], $this->sentJson(0));
+        $this->assertSame(['apply' => 'period_end', 'unit' => 'month', 'name' => 'Pro'], $this->sentJson(1));
+    }
+
+    public function test_a_refused_change_carries_its_error_code(): void
+    {
+        $this->respond(409, ['message' => 'The credit would exceed the open bill.', 'error' => 'credit_exceeds_bill']);
+
+        $subscription = new AppSubscription((object) $this->subscription(['active' => true])['data']);
+
+        try {
+            $subscription->change(['apply' => AppSubscription::APPLY_NOW, 'price' => '1.99']);
+            $this->fail('Expected an ApiException.');
+        } catch (ApiException $e) {
+            $this->assertTrue($e->isConflict());
+            $this->assertSame('credit_exceeds_bill', $e->error);
+        }
+    }
+
     public function test_a_missing_user_id_is_reported(): void
     {
         $this->expectException(InvalidArgumentException::class);
diff --git a/tests/Id/CheckoutConfirmationTest.php b/tests/Id/CheckoutConfirmationTest.php
index 92d385d..056e1e6 100644
--- a/tests/Id/CheckoutConfirmationTest.php
+++ b/tests/Id/CheckoutConfirmationTest.php
@@ -2,7 +2,9 @@
 
 namespace Anikeen\Id\Tests;
 
+use Anikeen\Id\AnikeenId;
 use Anikeen\Id\Billable;
+use Anikeen\Id\Exceptions\ApiException;
 use Anikeen\Id\Exceptions\ConfirmationRequiredException;
 use Illuminate\Database\Eloquent\Model;
 
@@ -60,4 +62,44 @@ class CheckoutConfirmationTest extends TestCase
             $this->assertSame('https://id.anikeen.com/checkout/subscriptions/01JSUB', $e->confirmationUrl);
         }
     }
+
+    public function test_a_trusted_app_lets_the_user_confirm_its_order(): void
+    {
+        $this->respond(201, ['data' => ['id' => '01JORD', 'status' => 'draft', 'group' => 'team-1', 'metadata' => ['topup' => '7'], 'expires_at' => '2026-11-05T10:00:00+00:00', 'confirmation_url' => 'https://id.anikeen.com/checkout/orders/01JORD']]);
+
+        $result = app(AnikeenId::class)->createOrderForUser('01JUSER', [
+            'group' => 'team-1',
+            'confirm' => true,
+            'return_url' => 'https://console.test/billing/topup',
+            'metadata' => ['topup' => '7'],
+            'items' => [['type' => 'digital', 'name' => 'Credit', 'unit' => 'onetime', 'units' => 1, 'gross_price' => '10.00']],
+        ]);
+
+        $this->assertSame('POST /api/v1/admin/orders Bearer app-token', $this->sent[0]['request']->getMethod() . ' ' . $this->sent[0]['request']->getUri()->getPath() . ' ' . $this->sent[0]['request']->getHeaderLine('Authorization'));
+        $this->assertTrue($this->sentJson(0)['confirm']);
+        $this->assertSame('https://console.test/billing/topup', $this->sentJson(0)['return_url']);
+        $this->assertSame(['topup' => '7'], $this->sentJson(0)['metadata']);
+        $this->assertSame('01JUSER', $this->sentJson(0)['user_id']);
+        $this->assertSame('https://id.anikeen.com/checkout/orders/01JORD', $result->data->confirmation_url);
+        $this->assertSame('7', $result->data->metadata->topup);
+    }
+
+    public function test_an_expired_confirmation_is_a_conflict(): void
+    {
+        $this->respond(200, ['data' => []]);
+        $this->respond(201, ['data' => ['id' => '01JORD', 'status' => 'draft', 'confirmation_url' => 'https://id.anikeen.com/checkout/orders/01JORD']]);
+        $this->respond(409, ['message' => 'The order was not confirmed in time.', 'error' => 'confirmation_expired']);
+
+        $order = $this->owner()->orders()->create(['confirm' => true, 'return_url' => 'https://shop.test/done', 'metadata' => ['cart' => 1], 'items' => []]);
+
+        $this->assertSame(['confirm' => true, 'return_url' => 'https://shop.test/done', 'metadata' => ['cart' => 1], 'items' => []], $this->sentJson(1));
+
+        try {
+            $order->checkout();
+            $this->fail('Expected an ApiException.');
+        } catch (ApiException $e) {
+            $this->assertTrue($e->isConflict());
+            $this->assertSame('confirmation_expired', $e->error);
+        }
+    }
 }
diff --git a/tests/Id/CheckoutSessionsTest.php b/tests/Id/CheckoutSessionsTest.php
index 06635f8..675adad 100644
--- a/tests/Id/CheckoutSessionsTest.php
+++ b/tests/Id/CheckoutSessionsTest.php
@@ -139,6 +139,32 @@ class CheckoutSessionsTest extends TestCase
         $this->assertNull($user->checkoutSessions()->find('unknown'));
     }
 
+    public function test_session_subscriptions_carry_a_free_trial(): void
+    {
+        $this->respond(201, $this->sessionData());
+
+        $this->owner()->appCheckoutSessions()->create(['subscriptions' => [
+            ['group' => 'team-1', 'name' => 'Pro', 'unit' => 'month', 'price' => '9.99', 'trial_days' => 14, 'trial_once' => true],
+            ['group' => 'team-1', 'name' => 'Backup', 'unit' => 'month', 'price' => '1.99', 'trial_ends_at' => '2026-12-01T00:00:00+00:00'],
+        ]]);
+
+        $this->assertSame(14, $this->sentJson(0)['subscriptions'][0]['trial_days']);
+        $this->assertTrue($this->sentJson(0)['subscriptions'][0]['trial_once']);
+        $this->assertSame('2026-12-01T00:00:00+00:00', $this->sentJson(0)['subscriptions'][1]['trial_ends_at']);
+    }
+
+    public function test_session_subscriptions_carry_a_discount(): void
+    {
+        $this->respond(201, $this->sessionData());
+
+        $this->owner()->checkoutSessions()->create(['subscriptions' => [
+            ['name' => 'Pro', 'unit' => 'month', 'price' => 4.99, 'discount' => ['label' => 'WELCOME', 'amount_off' => '1.00', 'duration' => 'once']],
+        ]]);
+
+        $this->assertSame('POST /api/v1/checkout-sessions Bearer user-token', $this->request(0));
+        $this->assertSame(['label' => 'WELCOME', 'amount_off' => '1.00', 'duration' => 'once'], $this->sentJson(0)['subscriptions'][0]['discount']);
+    }
+
     public function test_nothing_is_requested_until_a_method_is_called(): void
     {
         $this->owner()->checkoutSessions();
@@ -159,5 +185,8 @@ class CheckoutSessionsTest extends TestCase
         $this->assertSame(['01JS1', '01JS2'], $event['data']['object']['subscription_ids']);
         $this->assertContains('checkout.expired', EventType::all());
         $this->assertContains('subscription.activated', EventType::all());
+        $this->assertContains('subscription.trial_will_end', EventType::all());
+        $this->assertContains('subscription.discount_ended', EventType::all());
+        $this->assertContains('subscription.updated', EventType::all());
     }
 }
diff --git a/tests/Id/EndpointsTest.php b/tests/Id/EndpointsTest.php
index 7bd81bb..1fda366 100644
--- a/tests/Id/EndpointsTest.php
+++ b/tests/Id/EndpointsTest.php
@@ -246,6 +246,35 @@ class EndpointsTest extends TestCase
         $this->assertSame('POST /api/v1/admin/transactions Bearer app-token', $this->sentCall(1));
     }
 
+    public function test_billing_portal_links_for_users_use_the_app_token(): void
+    {
+        $link = ['object' => 'billing_portal_link', 'url' => 'https://id.test/billing/portal/01JUSER?signature=x', 'user_id' => '01JUSER', 'flow' => 'invoices', 'group' => 'team-1', 'return_url' => 'https://console.test/billing', 'expires_at' => '2026-11-04T10:15:00+00:00'];
+        $this->respond(201, ['data' => $link]);
+        $this->respond(201, ['data' => $link]);
+
+        $created = app(AnikeenId::class)->createBillingPortalLinkForUser('01JUSER', ['return_url' => 'https://console.test/billing', 'group' => 'team-1', 'flow' => 'invoices']);
+        $url = $this->owner()->appBillingPortalUrl(['flow' => 'payment_method_update']);
+
+        $this->assertSame('billing_portal_link', $created->object);
+        $this->assertSame($link['url'], $url);
+        $this->assertSame('POST /api/v1/client/users/01JUSER/billing-portal Bearer app-token', $this->sentCall(0));
+        $this->assertSame(['return_url' => 'https://console.test/billing', 'group' => 'team-1', 'flow' => 'invoices'], $this->sentJson(0));
+        $this->assertSame('POST /api/v1/client/users/01JUSER/billing-portal Bearer app-token', $this->sentCall(1));
+        $this->assertSame(['flow' => 'payment_method_update'], $this->sentJson(1));
+    }
+
+    public function test_a_refused_billing_portal_link_is_an_api_exception(): void
+    {
+        $this->respond(422, ['message' => 'The return URL has to point to one of the app\'s redirect URIs.', 'errors' => ['return_url' => ['…']]]);
+
+        try {
+            $this->owner()->appBillingPortalUrl(['return_url' => 'https://elsewhere.test']);
+            $this->fail('Expected an ApiException.');
+        } catch (ApiException $e) {
+            $this->assertSame(422, $e->status);
+        }
+    }
+
     public function test_order_preview_maps_the_country_into_the_billing_address(): void
     {
         $this->respond(200, ['data' => ['gross_total' => 11.9]]);
diff --git a/tests/Id/SubscriptionStatusTest.php b/tests/Id/SubscriptionStatusTest.php
index ddeca9c..25eba66 100644
--- a/tests/Id/SubscriptionStatusTest.php
+++ b/tests/Id/SubscriptionStatusTest.php
@@ -47,6 +47,7 @@ class SubscriptionStatusTest extends TestCase
             $this->assertSame($status, $resource->status());
             $this->assertSame($running, $resource->isActive());
             $this->assertSame($status === SubscriptionStatus::DRAFT, $resource->isDraft());
+            $this->assertSame($status === SubscriptionStatus::TRIAL, $resource->isTrial());
             $this->assertSame($status === SubscriptionStatus::PAUSED, $resource->isPaused());
             $this->assertSame($status === SubscriptionStatus::CANCELLING, $resource->isCancelling());
             $this->assertSame($status === SubscriptionStatus::EXPIRED, $resource->isExpired());
diff --git a/tests/Id/WebhookTest.php b/tests/Id/WebhookTest.php
index ab0bb88..d9e75b0 100644
--- a/tests/Id/WebhookTest.php
+++ b/tests/Id/WebhookTest.php
@@ -3,6 +3,7 @@
 namespace Anikeen\Id\Tests;
 
 use Anikeen\Id\Exceptions\SignatureVerificationException;
+use Anikeen\Id\Webhooks\EventType;
 use Anikeen\Id\Webhooks\Webhook;
 
 class WebhookTest extends TestCase
@@ -53,4 +54,31 @@ class WebhookTest extends TestCase
 
         Webhook::constructEvent($this->payload, null, $this->secret);
     }
+
+    public function test_a_renewal_carries_the_booked_period(): void
+    {
+        $this->payload = json_encode(['id' => '01JEVT', 'type' => EventType::SUBSCRIPTION_RENEWED, 'created' => time(), 'data' => [
+            'object' => ['id' => '01JSUB', 'status' => 'active'],
+            'period' => ['object' => 'subscription_period', 'subscription_id' => '01JSUB', 'period_start' => '2026-11-01T00:00:00+00:00', 'period_end' => '2026-12-01T00:00:00+00:00', 'periods' => 1, 'first_period' => true, 'unit' => 'month', 'order_id' => '01JORD', 'order_item_id' => '01JITEM', 'items' => [], 'currency_iso' => 'EUR', 'net_amount' => 8],
+        ]]);
+
+        $event = Webhook::constructEvent($this->payload, $this->header(), $this->secret);
+
+        $this->assertSame('subscription.renewed', $event['type']);
+        $this->assertSame('01JORD', $event['data']['period']['order_id']);
+        $this->assertTrue($event['data']['period']['first_period']);
+        $this->assertContains(EventType::SUBSCRIPTION_RENEWED, EventType::all());
+    }
+
+    public function test_a_change_carries_the_previous_attributes(): void
+    {
+        $this->payload = json_encode(['id' => '01JEVT', 'type' => EventType::SUBSCRIPTION_UPDATED, 'created' => time(), 'data' => [
+            'object' => ['id' => '01JSUB', 'price' => 14.99],
+            'previous_attributes' => ['price' => 9.99],
+        ]]);
+
+        $event = Webhook::constructEvent($this->payload, $this->header(), $this->secret);
+
+        $this->assertSame(9.99, $event['data']['previous_attributes']['price']);
+    }
 }