diff --git a/README.md b/README.md
index 5dfa60d..709f742 100644
--- a/README.md
+++ b/README.md
@@ -361,8 +361,31 @@ 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. Cancelling during the trial
+bills nothing. Trials work the same for app subscriptions and per subscription of a checkout
+session.
 
 ### Webhooks
 
@@ -508,7 +531,7 @@ subscriptions it created (plus those of clients delegated to it).
 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`) and `isNotFound()`, `isConflict()`, `isTemporary()`:
+`idempotency_key_conflict`, `in_checkout_session`, `trial_already_used`) and `isNotFound()`, `isConflict()`, `isTemporary()`:
 
 ```php
 try {
diff --git a/README.stub b/README.stub
index c87d48b..b03c161 100644
--- a/README.stub
+++ b/README.stub
@@ -361,8 +361,31 @@ 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. Cancelling during the trial
+bills nothing. Trials work the same for app subscriptions and per subscription of a checkout
+session.
 
 ### Webhooks
 
@@ -508,7 +531,7 @@ subscriptions it created (plus those of clients delegated to it).
 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`) and `isNotFound()`, `isConflict()`, `isTemporary()`:
+`idempotency_key_conflict`, `in_checkout_session`, `trial_already_used`) and `isNotFound()`, `isConflict()`, `isTemporary()`:
 
 ```php
 try {
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/Resources/AppCheckoutSessions.php b/src/Id/Resources/AppCheckoutSessions.php
index 5c479f4..02ca49f 100644
--- a/src/Id/Resources/AppCheckoutSessions.php
+++ b/src/Id/Resources/AppCheckoutSessions.php
@@ -36,7 +36,10 @@ 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
      *     }>,
      *     return_url?: null|string,
      *     metadata?: null|array,
@@ -45,6 +48,8 @@ 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.
      *
      * @throws ApiException 422 validation (e.g. return_url), 409 "idempotency_key_conflict"
      */
diff --git a/src/Id/Resources/AppSubscriptions.php b/src/Id/Resources/AppSubscriptions.php
index 777da58..35066cb 100644
--- a/src/Id/Resources/AppSubscriptions.php
+++ b/src/Id/Resources/AppSubscriptions.php
@@ -49,6 +49,9 @@ class AppSubscriptions
      *     vat_rate?: float,
      *     payload?: null|array,
      *     ends_at?: null|string,
+     *     trial_days?: null|int,
+     *     trial_ends_at?: null|string,
+     *     trial_once?: bool,
      *     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 +59,13 @@ 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).
      *
-     * @throws ApiException
+     * @throws ApiException 422 validation, 409 "idempotency_key_conflict", …
      */
     public function create(array $attributes): AppSubscription
     {
diff --git a/src/Id/Resources/Subscriptions.php b/src/Id/Resources/Subscriptions.php
index 9b2a0f9..7cd5305 100644
--- a/src/Id/Resources/Subscriptions.php
+++ b/src/Id/Resources/Subscriptions.php
@@ -24,7 +24,10 @@ 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
      *  } $attributes The subscription data:
      *    - group:          The group (optional)
      *    - name:           The name
@@ -36,6 +39,9 @@ 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)
      * @throws Throwable
      */
     public function create(array $attributes): Subscription
diff --git a/src/Id/Webhooks/EventType.php b/src/Id/Webhooks/EventType.php
index e4b8b44..3fcd1af 100644
--- a/src/Id/Webhooks/EventType.php
+++ b/src/Id/Webhooks/EventType.php
@@ -21,6 +21,9 @@ final class EventType
     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. */
+    public const SUBSCRIPTION_TRIAL_WILL_END = 'subscription.trial_will_end';
+
     /** 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/AppSubscriptionsTest.php b/tests/Id/AppSubscriptionsTest.php
index 53e41ef..4132ff0 100644
--- a/tests/Id/AppSubscriptionsTest.php
+++ b/tests/Id/AppSubscriptionsTest.php
@@ -174,6 +174,35 @@ 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_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_missing_user_id_is_reported(): void
     {
         $this->expectException(InvalidArgumentException::class);
diff --git a/tests/Id/CheckoutSessionsTest.php b/tests/Id/CheckoutSessionsTest.php
index 06635f8..5b38e78 100644
--- a/tests/Id/CheckoutSessionsTest.php
+++ b/tests/Id/CheckoutSessionsTest.php
@@ -139,6 +139,20 @@ 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_nothing_is_requested_until_a_method_is_called(): void
     {
         $this->owner()->checkoutSessions();
@@ -159,5 +173,6 @@ 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());
     }
 }
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());