diff --git a/app/Http/Controllers/App/WorkspaceController.php b/app/Http/Controllers/App/WorkspaceController.php
index d9d394ff..5b2326f2 100644
--- a/app/Http/Controllers/App/WorkspaceController.php
+++ b/app/Http/Controllers/App/WorkspaceController.php
@@ -15,6 +15,7 @@
 use App\Http\Requests\App\Workspace\StoreWorkspaceRequest;
 use App\Http\Requests\App\Workspace\UpdateWorkspaceRequest;
 use App\Http\Resources\App\WorkspaceMemberResource;
+use App\Models\User;
 use App\Models\Workspace;
 use App\Services\Brand\LogoAttacher;
 use Illuminate\Http\JsonResponse;
@@ -66,13 +67,8 @@ public function index(Request $request): Response
 
     public function create(Request $request): Response|RedirectResponse
     {
-        $user = $request->user();
-
-        if (! config('trypost.self_hosted')
-            && $user->ownedWorkspacesCount() > 0
-            && ! $user->account?->hasActiveSubscription()) {
-            return redirect()->route('app.billing.index')
-                ->with('message', 'Subscribe to create more workspaces.');
+        if ($redirect = $this->denyAdditionalWorkspaceWithoutSubscription($request->user())) {
+            return $redirect;
         }
 
         return Inertia::render('workspaces/Create', [
@@ -83,6 +79,24 @@ public function create(Request $request): Response|RedirectResponse
         ]);
     }
 
+    /**
+     * Block creating a paid additional workspace without an active subscription.
+     * Guards both the form (`create`) and the write (`store`) so a direct POST
+     * can't bootstrap a second billable workspace — which would also inflate the
+     * checkout quantity past the fixed first-month coupon.
+     */
+    private function denyAdditionalWorkspaceWithoutSubscription(User $user): ?RedirectResponse
+    {
+        if (! config('trypost.self_hosted')
+            && $user->ownedWorkspacesCount() > 0
+            && ! $user->account?->hasActiveSubscription()) {
+            return redirect()->route('app.billing.index')
+                ->with('message', 'Subscribe to create more workspaces.');
+        }
+
+        return null;
+    }
+
     public function autofillBrand(AutofillBrandRequest $request, AutofillBrand $autofill): JsonResponse
     {
         try {
@@ -98,6 +112,10 @@ public function store(StoreWorkspaceRequest $request, LogoAttacher $logoAttacher
     {
         $user = $request->user();
 
+        if ($redirect = $this->denyAdditionalWorkspaceWithoutSubscription($user)) {
+            return $redirect;
+        }
+
         $validated = $request->validated();
 
         $workspace = CreateWorkspace::execute($user, $validated);
diff --git a/app/Support/Billing/FirstMonthCheckoutDiscount.php b/app/Support/Billing/FirstMonthCheckoutDiscount.php
index 9f69ff85..064a27dd 100644
--- a/app/Support/Billing/FirstMonthCheckoutDiscount.php
+++ b/app/Support/Billing/FirstMonthCheckoutDiscount.php
@@ -5,6 +5,7 @@
 namespace App\Support\Billing;
 
 use Laravel\Cashier\SubscriptionBuilder;
+use RuntimeException;
 
 final class FirstMonthCheckoutDiscount
 {
@@ -14,13 +15,26 @@ final class FirstMonthCheckoutDiscount
      * instead of a $0 trial authorization. Stripe rejects a Checkout Session
      * that sets both `discounts` and `allow_promotion_codes`, so accounts that
      * skip the paid first month keep the promotion-code field instead.
+     *
+     * @throws RuntimeException when the paid first month is enabled but no
+     *                          coupon is configured — failing loudly beats
+     *                          silently charging every new customer full price.
      */
     public static function apply(SubscriptionBuilder $subscription): SubscriptionBuilder
     {
-        if ((bool) config('trypost.billing.require_card_for_trial', true)) {
-            return $subscription->withCoupon(config('cashier.first_month_coupon_id'));
+        if (! (bool) config('trypost.billing.require_card_for_trial', true)) {
+            return $subscription->allowPromotionCodes();
         }
 
-        return $subscription->allowPromotionCodes();
+        $couponId = config('cashier.first_month_coupon_id');
+
+        if (! is_string($couponId) || $couponId === '') {
+            throw new RuntimeException(
+                'STRIPE_FIRST_MONTH_COUPON_ID must be set when REQUIRE_CARD_FOR_TRIAL is enabled, '
+                .'otherwise checkout would charge the full price instead of the $1 first month.'
+            );
+        }
+
+        return $subscription->withCoupon($couponId);
     }
 }
diff --git a/tests/Feature/WorkspaceControllerTest.php b/tests/Feature/WorkspaceControllerTest.php
index 796bef21..e1354dc5 100644
--- a/tests/Feature/WorkspaceControllerTest.php
+++ b/tests/Feature/WorkspaceControllerTest.php
@@ -677,6 +677,26 @@
     expect(Workspace::where('account_id', $account->id)->count())->toBe(2);
 });
 
+test('store blocks a second workspace without an active subscription', function () {
+    config(['trypost.self_hosted' => false]);
+
+    $account = Account::factory()->create();
+    $user = User::factory()->create(['account_id' => $account->id]);
+    $account->update(['owner_id' => $user->id]);
+
+    // The account already owns one workspace and has no subscription, so a
+    // direct POST must not bootstrap a second (billable) workspace.
+    $existing = Workspace::factory()->create(['account_id' => $account->id, 'user_id' => $user->id]);
+    $existing->members()->attach($user->id, ['role' => Role::Member->value]);
+
+    $response = $this->actingAs($user)->post(route('app.workspaces.store'), [
+        'name' => 'Second Workspace',
+    ]);
+
+    $response->assertRedirect(route('app.billing.index'));
+    expect(Workspace::where('account_id', $account->id)->count())->toBe(1);
+});
+
 test('store attaches logo when logo_url is provided', function () {
     $account = Account::factory()->create();
     $user = User::factory()->create(['account_id' => $account->id]);
diff --git a/tests/Unit/Support/Billing/FirstMonthCheckoutDiscountTest.php b/tests/Unit/Support/Billing/FirstMonthCheckoutDiscountTest.php
index b1dc7fd6..21738c2c 100644
--- a/tests/Unit/Support/Billing/FirstMonthCheckoutDiscountTest.php
+++ b/tests/Unit/Support/Billing/FirstMonthCheckoutDiscountTest.php
@@ -37,3 +37,17 @@
     expect($subscription->allowPromotionCodes)->toBeTrue()
         ->and($subscription->couponId)->toBeNull();
 });
+
+test('throws instead of charging full price when the coupon is missing but a card is required', function () {
+    config([
+        'trypost.billing.require_card_for_trial' => true,
+        'cashier.first_month_coupon_id' => '',
+    ]);
+
+    $subscription = $this->account->newSubscription(Account::SUBSCRIPTION_NAME, 'price_monthly_test');
+
+    expect(fn () => FirstMonthCheckoutDiscount::apply($subscription))
+        ->toThrow(RuntimeException::class);
+
+    expect($subscription->couponId)->toBeNull();
+});