diff --git a/app/Models/UserPaymentOption.php b/app/Models/UserPaymentOption.php
index a783a0fc..4e29bd45 100644
--- a/app/Models/UserPaymentOption.php
+++ b/app/Models/UserPaymentOption.php
@@ -80,12 +80,26 @@ class UserPaymentOption extends Model
     }
 
     /**
-     * Laufender Bestandsschutz (Grandfathered mit gültigem grandfathered_until).
+     * Laufender Bestandsschutz. `grandfathered_until` ist das explizite
+     * Legacy-Vertragsende (valid_until_date) und deckelt, wenn gesetzt.
+     * Bei offenen Dauervereinbarungen ist es NULL (Regelfall im Import) —
+     * dann zählt die laufende, vom MAN-Rechnungslauf fortgerollte Periode
+     * (`current_period_end` = next_due_date). Fix 06.07.2026: vorher galt
+     * NULL pauschal als abgelaufen, wodurch praktisch kein Legacy-Kunde
+     * eine aktive Zahlungsoption hatte („Buchung erforderlich").
      */
     public function scopeGrandfatheredNow(Builder $query): Builder
     {
         return $query
             ->where('status', UserPaymentOptionStatus::Grandfathered->value)
-            ->whereDate('grandfathered_until', '>=', now());
+            ->where(function (Builder $query): void {
+                $query
+                    ->whereDate('grandfathered_until', '>=', now())
+                    ->orWhere(function (Builder $rolling): void {
+                        $rolling
+                            ->whereNull('grandfathered_until')
+                            ->whereDate('current_period_end', '>=', now());
+                    });
+            });
     }
 }
diff --git a/tests/Feature/Billing/HasActiveBookingTest.php b/tests/Feature/Billing/HasActiveBookingTest.php
index c346c658..6760e6aa 100644
--- a/tests/Feature/Billing/HasActiveBookingTest.php
+++ b/tests/Feature/Billing/HasActiveBookingTest.php
@@ -118,8 +118,10 @@ test('a grandfathered agreement with expired protection does not count as bookin
     expect($user->hasActiveBooking())->toBeFalse();
 });
 
-test('a grandfathered agreement without an end date does not count as booking', function () {
-    // NULL = abgelaufen/ungültig (User-Entscheidung 19.06.2026).
+test('a grandfathered agreement without an end date counts while its period is running', function () {
+    // Regelfall des Imports (Fix 06.07.2026): offene Dauervereinbarung —
+    // grandfathered_until NULL, Gültigkeit über die laufende Periode
+    // (current_period_end = next_due_date, vom MAN-Lauf fortgerollt).
     $user = User::factory()->create();
 
     UserPaymentOption::factory()->create([
@@ -127,6 +129,43 @@ test('a grandfathered agreement without an end date does not count as booking',
         'payment_option_id' => PaymentOption::factory()->create()->id,
         'status' => UserPaymentOptionStatus::Grandfathered->value,
         'grandfathered_until' => null,
+        'current_period_start' => now()->subMonths(3),
+        'current_period_end' => now()->addMonths(9),
+        'stripe_subscription_id' => null,
+    ]);
+
+    expect($user->hasActiveBooking())->toBeTrue();
+});
+
+test('a grandfathered agreement without an end date lapses with its period', function () {
+    $user = User::factory()->create();
+
+    UserPaymentOption::factory()->create([
+        'user_id' => $user->id,
+        'payment_option_id' => PaymentOption::factory()->create()->id,
+        'status' => UserPaymentOptionStatus::Grandfathered->value,
+        'grandfathered_until' => null,
+        'current_period_start' => now()->subYears(2),
+        'current_period_end' => now()->subYear(),
+        'stripe_subscription_id' => null,
+    ]);
+
+    expect($user->hasActiveBooking())->toBeFalse();
+});
+
+test('an explicit legacy end date caps a grandfathered agreement despite a running period', function () {
+    // grandfathered_until = explizites Vertragsende (valid_until_date) —
+    // wenn gesetzt und überschritten, zählt die Vereinbarung nicht mehr,
+    // auch wenn die Abrechnungsperiode formal noch läuft.
+    $user = User::factory()->create();
+
+    UserPaymentOption::factory()->create([
+        'user_id' => $user->id,
+        'payment_option_id' => PaymentOption::factory()->create()->id,
+        'status' => UserPaymentOptionStatus::Grandfathered->value,
+        'grandfathered_until' => now()->subDay(),
+        'current_period_start' => now()->subMonths(3),
+        'current_period_end' => now()->addMonths(9),
         'stripe_subscription_id' => null,
     ]);