diff --git a/app/Domains/Purchase/Controllers/PurchaseController.php b/app/Domains/Purchase/Controllers/PurchaseController.php
index 930ef48..4d25a08 100644
--- a/app/Domains/Purchase/Controllers/PurchaseController.php
+++ b/app/Domains/Purchase/Controllers/PurchaseController.php
@@ -12,6 +12,7 @@ use App\Domains\Purchase\Requests\UpdatePurchaseItemRequest;
 use App\Domains\Purchase\Resources\PurchaseResource;
 use App\Domains\Purchase\Services\Checkout\PurchaseResponseLoader;
 use App\Domains\Purchase\Services\CheckoutService;
+use App\Domains\Purchase\Services\PurchaseStateGuard;
 use App\Domains\Tenant\Models\Tenant;
 use App\Http\Controllers\Controller;
 use Illuminate\Http\JsonResponse;
@@ -132,42 +133,48 @@ class PurchaseController extends Controller
         Tenant $tenant,
         Purchase $compra,
         CheckoutService $checkoutService,
+        PurchaseStateGuard $purchaseState,
     ): JsonResponse {
         $compra = $this->resolveScopedPurchase($tenant, $request->user()->id, $compra);
         $method = $request->validated('method');
-        $totalAmount = $compra->calculateCurrentTotalAmount();
+        $transferPayerDni = $method === 'transfer'
+            ? preg_replace('/\D+/', '', (string) $request->validated('transfer_payer_dni'))
+            : null;
 
-        $purchaseUpdate = [
-            'payment_method' => $method,
-            'status' => Purchase::STATUS_PENDING_PAYMENT,
-            'expires_at' => now()->addMinutes(
-                max(1, (int) config("purchase.payment_expiration_minutes.{$method}", 30))
-            ),
-            'total' => $totalAmount,
-        ];
-
-        if ($method === 'transfer') {
-            $purchaseUpdate['transfer_payer_dni'] = preg_replace('/\D+/', '', (string) $request->validated('transfer_payer_dni'));
-        }
-
-        $updated = DB::transaction(function () use ($compra, $purchaseUpdate): bool {
+        $updated = DB::transaction(function () use ($compra, $method, $purchaseState, $transferPayerDni): bool {
             /** @var Purchase|null $purchase */
             $purchase = Purchase::query()
                 ->whereKey($compra->getKey())
                 ->lockForUpdate()
                 ->first();
 
+            if ($purchase === null) {
+                return false;
+            }
+
+            $purchaseState->assertNotExpired($purchase);
+
             if (
-                $purchase === null
-                || ! in_array($purchase->status, [
+                ! in_array($purchase->status, [
                     Purchase::STATUS_CREATED,
                     Purchase::STATUS_PENDING_PAYMENT,
                 ], true)
-                || ($purchase->expires_at !== null && $purchase->expires_at->isPast())
             ) {
                 return false;
             }
 
+            $purchaseUpdate = [
+                'payment_method' => $method,
+                'status' => Purchase::STATUS_PENDING_PAYMENT,
+                'expires_at' => now()->addMinutes(
+                    max(1, (int) config("purchase.payment_expiration_minutes.{$method}", 30))
+                ),
+                'total' => $purchase->calculateCurrentTotalAmount(),
+            ];
+
+            if ($transferPayerDni !== null) {
+                $purchaseUpdate['transfer_payer_dni'] = $transferPayerDni;
+            }
             $purchase->update($purchaseUpdate);
 
             return true;
@@ -180,6 +187,7 @@ class PurchaseController extends Controller
         }
 
         $compra->refresh();
+        $totalAmount = (float) $compra->total;
         $checkoutService->syncReservationExpiration($compra);
 
         if ($method === 'transfer') {
diff --git a/app/Domains/Purchase/Exceptions/PurchaseExpiredException.php b/app/Domains/Purchase/Exceptions/PurchaseExpiredException.php
new file mode 100644
index 0000000..629148f
--- /dev/null
+++ b/app/Domains/Purchase/Exceptions/PurchaseExpiredException.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace App\Domains\Purchase\Exceptions;
+
+use RuntimeException;
+
+class PurchaseExpiredException extends RuntimeException
+{
+    public function __construct()
+    {
+        parent::__construct(__('api.purchase.expired'));
+    }
+}
diff --git a/app/Domains/Purchase/Services/Checkout/CompleteCheckoutService.php b/app/Domains/Purchase/Services/Checkout/CompleteCheckoutService.php
index adbfd58..efafde2 100644
--- a/app/Domains/Purchase/Services/Checkout/CompleteCheckoutService.php
+++ b/app/Domains/Purchase/Services/Checkout/CompleteCheckoutService.php
@@ -5,6 +5,7 @@ namespace App\Domains\Purchase\Services\Checkout;
 use App\Domains\Cart\Models\CartItem;
 use App\Domains\Catalog\Services\StockReservationService;
 use App\Domains\Purchase\Models\Purchase;
+use App\Domains\Purchase\Services\PurchaseStateGuard;
 use Illuminate\Support\Collection;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Validation\ValidationException;
@@ -15,12 +16,14 @@ class CompleteCheckoutService
         private readonly StockReservationService $reservations,
         private readonly SourceCartService $sourceCart,
         private readonly PurchaseItemSnapshotFactory $snapshots,
+        private readonly PurchaseStateGuard $purchaseState,
     ) {}
 
     public function complete(Purchase $purchase): Purchase
     {
         return DB::transaction(function () use ($purchase): Purchase {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
 
             if ($purchase->payment_method === null) {
                 throw ValidationException::withMessages([
@@ -45,6 +48,7 @@ class CompleteCheckoutService
     {
         return DB::transaction(function () use ($purchase): Purchase {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
 
             if ($purchase->status === Purchase::STATUS_PAID) {
                 return $this->loadPurchase($purchase);
@@ -70,6 +74,7 @@ class CompleteCheckoutService
     {
         DB::transaction(function () use ($purchase): void {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
 
             if ($purchase->status === Purchase::STATUS_PAID) {
                 return;
diff --git a/app/Domains/Purchase/Services/Checkout/EditCheckoutService.php b/app/Domains/Purchase/Services/Checkout/EditCheckoutService.php
index 4b6aa33..58e7ec9 100644
--- a/app/Domains/Purchase/Services/Checkout/EditCheckoutService.php
+++ b/app/Domains/Purchase/Services/Checkout/EditCheckoutService.php
@@ -6,6 +6,7 @@ use App\Domains\Catalog\Models\Variant;
 use App\Domains\Catalog\Services\CatalogInventoryService;
 use App\Domains\Purchase\Models\Purchase;
 use App\Domains\Purchase\Models\PurchaseItem;
+use App\Domains\Purchase\Services\PurchaseStateGuard;
 use App\Domains\Purchase\Services\UserPurchaseLimitService;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Validation\ValidationException;
@@ -20,6 +21,7 @@ class EditCheckoutService
         private readonly SourceCartService $sourceCart,
         private readonly PurchaseItemSnapshotFactory $snapshots,
         private readonly PurchaseResponseLoader $responses,
+        private readonly PurchaseStateGuard $purchaseState,
     ) {}
 
     /** @param array<string, string> $customerData */
@@ -27,6 +29,7 @@ class EditCheckoutService
     {
         return DB::transaction(function () use ($purchase, $customerData): Purchase {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
             $this->assertEditable($purchase);
 
             $purchase->update($customerData);
@@ -50,6 +53,7 @@ class EditCheckoutService
             $updateVariant,
         ): Purchase {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
 
             if ($purchase->status !== Purchase::STATUS_CREATED || $this->hasExpired($purchase)) {
                 throw ValidationException::withMessages([
@@ -182,6 +186,7 @@ class EditCheckoutService
     {
         return DB::transaction(function () use ($purchase): Purchase {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
             $this->assertEditable($purchase);
 
             if (! $purchase->tenant()->firstOrFail()->checkout_editing_policy->allowsModification()) {
@@ -208,6 +213,7 @@ class EditCheckoutService
     {
         return DB::transaction(function () use ($purchase, $purchaseItem): Purchase {
             $purchase = $this->lockPurchase($purchase);
+            $this->purchaseState->assertNotExpired($purchase);
             $this->assertEditable($purchase);
 
             if (! $purchase->tenant()->firstOrFail()->checkout_editing_policy->allowsRemoval()) {
diff --git a/app/Domains/Purchase/Services/Checkout/ReleaseCheckoutService.php b/app/Domains/Purchase/Services/Checkout/ReleaseCheckoutService.php
index bdf17a4..77870d6 100644
--- a/app/Domains/Purchase/Services/Checkout/ReleaseCheckoutService.php
+++ b/app/Domains/Purchase/Services/Checkout/ReleaseCheckoutService.php
@@ -5,6 +5,7 @@ namespace App\Domains\Purchase\Services\Checkout;
 use App\Domains\Catalog\Models\StockReservation;
 use App\Domains\Catalog\Services\StockReservationService;
 use App\Domains\Purchase\Models\Purchase;
+use App\Domains\Purchase\Services\PurchaseStateGuard;
 use Illuminate\Support\Facades\DB;
 use Illuminate\Support\Facades\Log;
 use Illuminate\Validation\ValidationException;
@@ -14,6 +15,8 @@ class ReleaseCheckoutService
 {
     public function __construct(
         private readonly StockReservationService $reservations,
+        private readonly SourceCartService $sourceCart,
+        private readonly PurchaseStateGuard $purchaseState,
     ) {}
 
     public function cancel(Purchase $purchase): Purchase
@@ -70,6 +73,10 @@ class ReleaseCheckoutService
         return DB::transaction(function () use ($purchase, $targetStatus): Purchase {
             $purchase = $this->lockPurchase($purchase);
 
+            if ($targetStatus !== Purchase::STATUS_EXPIRED) {
+                $this->purchaseState->assertNotExpired($purchase);
+            }
+
             if ($purchase->status === Purchase::STATUS_PAID) {
                 if ($targetStatus === Purchase::STATUS_EXPIRED) {
                     return $this->loadPurchase($purchase);
diff --git a/app/Domains/Purchase/Services/PurchaseStateGuard.php b/app/Domains/Purchase/Services/PurchaseStateGuard.php
new file mode 100644
index 0000000..45e8b92
--- /dev/null
+++ b/app/Domains/Purchase/Services/PurchaseStateGuard.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Domains\Purchase\Services;
+
+use App\Domains\Purchase\Exceptions\PurchaseExpiredException;
+use App\Domains\Purchase\Models\Purchase;
+
+class PurchaseStateGuard
+{
+    public function assertNotExpired(Purchase $purchase): void
+    {
+        $hasExpiredStatus = $purchase->status === Purchase::STATUS_EXPIRED;
+        $hasExpiredByTime = in_array($purchase->status, [
+            Purchase::STATUS_CREATED,
+            Purchase::STATUS_PENDING_PAYMENT,
+        ], true)
+            && $purchase->expires_at !== null
+            && $purchase->expires_at->isPast();
+
+        if ($hasExpiredStatus || $hasExpiredByTime) {
+            throw new PurchaseExpiredException;
+        }
+    }
+}
diff --git a/bootstrap/app.php b/bootstrap/app.php
index da41ac0..6159d8d 100644
--- a/bootstrap/app.php
+++ b/bootstrap/app.php
@@ -2,6 +2,7 @@
 
 use App\Domains\Auth\Exceptions\AccountLockedException;
 use App\Domains\Purchase\Exceptions\InsufficientStockException;
+use App\Domains\Purchase\Exceptions\PurchaseExpiredException;
 use App\Domains\Purchase\Exceptions\PurchaseLimitExceededException;
 use App\Domains\Ticket\Exceptions\TicketNotAvailableException;
 use App\Http\Middleware\EnsureAdminAppTenant;
@@ -102,6 +103,16 @@ return Application::configure(basePath: dirname(__DIR__))
                 'maximum_addable_quantity' => $exception->maximumAddableQuantity,
             ], 422);
         });
+        $exceptions->render(function (PurchaseExpiredException $exception, Request $request) {
+            if (! $request->is('api/*')) {
+                return null;
+            }
+
+            return response()->json([
+                'code' => 'purchase.expired',
+                'message' => $exception->getMessage(),
+            ], 422);
+        });
         $exceptions->render(function (ModelNotFoundException $exception, Request $request) {
             if (! $request->is('api/*')) {
                 return null;
diff --git a/lang/en/api.php b/lang/en/api.php
index aa37385..f0356ed 100644
--- a/lang/en/api.php
+++ b/lang/en/api.php
@@ -36,6 +36,7 @@ return [
         'variant_required' => 'You must select a variant for this item.',
     ],
     'purchase' => [
+        'expired' => 'The purchase has expired. Please start a new purchase.',
         'variant_change_disabled' => 'Variant changes are disabled for this purchase.',
         'source_required' => 'A cart or direct item is required.',
         'payment_method_required' => 'The purchase payment method must be selected before finalizing.',
diff --git a/lang/es/api.php b/lang/es/api.php
index 1fb1596..bfa17c4 100644
--- a/lang/es/api.php
+++ b/lang/es/api.php
@@ -36,6 +36,7 @@ return [
         'variant_required' => 'Debe seleccionar una variante para este ítem.',
     ],
     'purchase' => [
+        'expired' => "La compra venci\u{00F3}. Inici\u{00E1} una nueva compra.",
         'variant_change_disabled' => 'El cambio de variante está deshabilitado para esta compra.',
         'source_required' => 'Se requiere un carrito o un producto directo.',
         'payment_method_required' => 'Debes seleccionar el método de pago antes de finalizar la compra.',
diff --git a/tests/Feature/Purchase/PurchaseExpiredExceptionResponseTest.php b/tests/Feature/Purchase/PurchaseExpiredExceptionResponseTest.php
new file mode 100644
index 0000000..49e4522
--- /dev/null
+++ b/tests/Feature/Purchase/PurchaseExpiredExceptionResponseTest.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Tests\Feature\Purchase;
+
+use App\Domains\Purchase\Exceptions\PurchaseExpiredException;
+use Illuminate\Support\Facades\Route;
+use Tests\TestCase;
+
+class PurchaseExpiredExceptionResponseTest extends TestCase
+{
+    public function test_it_returns_a_stable_api_error_for_an_expired_purchase(): void
+    {
+        Route::get('/api/test/purchase-expired', function (): never {
+            throw new PurchaseExpiredException;
+        });
+
+        $this->getJson('/api/test/purchase-expired')
+            ->assertUnprocessable()
+            ->assertExactJson([
+                'code' => 'purchase.expired',
+                'message' => __('api.purchase.expired'),
+            ]);
+    }
+}
diff --git a/tests/Unit/Purchase/PurchaseStateGuardTest.php b/tests/Unit/Purchase/PurchaseStateGuardTest.php
new file mode 100644
index 0000000..f083fdd
--- /dev/null
+++ b/tests/Unit/Purchase/PurchaseStateGuardTest.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace Tests\Unit\Purchase;
+
+use App\Domains\Purchase\Exceptions\PurchaseExpiredException;
+use App\Domains\Purchase\Models\Purchase;
+use App\Domains\Purchase\Services\PurchaseStateGuard;
+use Tests\TestCase;
+
+class PurchaseStateGuardTest extends TestCase
+{
+    private PurchaseStateGuard $guard;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->guard = new PurchaseStateGuard;
+    }
+
+    public function test_it_rejects_a_purchase_with_expired_status(): void
+    {
+        $purchase = (new Purchase)->forceFill([
+            'status' => Purchase::STATUS_EXPIRED,
+            'expires_at' => null,
+        ]);
+
+        $this->expectException(PurchaseExpiredException::class);
+
+        $this->guard->assertNotExpired($purchase);
+    }
+
+    public function test_it_rejects_an_active_purchase_when_its_deadline_has_passed(): void
+    {
+        $purchase = (new Purchase)->forceFill([
+            'status' => Purchase::STATUS_PENDING_PAYMENT,
+            'expires_at' => now()->subMinute(),
+        ]);
+
+        $this->expectException(PurchaseExpiredException::class);
+
+        $this->guard->assertNotExpired($purchase);
+    }
+
+    public function test_it_does_not_treat_a_paid_purchase_as_expired_by_time(): void
+    {
+        $purchase = (new Purchase)->forceFill([
+            'status' => Purchase::STATUS_PAID,
+            'expires_at' => now()->subMinute(),
+        ]);
+
+        $this->guard->assertNotExpired($purchase);
+
+        $this->assertTrue(true);
+    }
+}