diff --git a/src/app/Http/Controllers/API/V4/PaymentsController.php b/src/app/Http/Controllers/API/V4/PaymentsController.php
--- a/src/app/Http/Controllers/API/V4/PaymentsController.php
+++ b/src/app/Http/Controllers/API/V4/PaymentsController.php
@@ -21,7 +21,7 @@
         $user = Auth::guard()->user();
 
         // TODO: Wallet selection
-        $wallet = $user->wallets->first();
+        $wallet = $user->wallets()->first();
 
         $mandate = self::walletMandate($wallet);
 
@@ -40,28 +40,10 @@
         $current_user = Auth::guard()->user();
 
         // TODO: Wallet selection
-        $wallet = $current_user->wallets->first();
+        $wallet = $current_user->wallets()->first();
 
-        $rules = [
-            'amount' => 'required|numeric',
-            'balance' => 'required|numeric|min:0',
-        ];
-
-        // Check required fields
-        $v = Validator::make($request->all(), $rules);
-
-        // TODO: allow comma as a decimal point?
-
-        if ($v->fails()) {
-            return response()->json(['status' => 'error', 'errors' => $v->errors()], 422);
-        }
-
-        $amount = (int) ($request->amount * 100);
-
-        // Validate the minimum value
-        if ($amount < PaymentProvider::MIN_AMOUNT) {
-            $min = intval(PaymentProvider::MIN_AMOUNT / 100) . ' CHF';
-            $errors = ['amount' => \trans('validation.minamount', ['amount' => $min])];
+        // Input validation
+        if ($errors = self::mandateValidate($request, $wallet)) {
             return response()->json(['status' => 'error', 'errors' => $errors], 422);
         }
 
@@ -70,15 +52,20 @@
                 'mandate_balance' => $request->balance,
         ]);
 
-        $request = [
+        $mandate = [
             'currency' => 'CHF',
-            'amount' => $amount,
             'description' => \config('app.name') . ' Auto-Payment Setup',
         ];
 
+        // Normally the auto-payment setup operation is 0, if the balance is below the threshold
+        // we'll top-up the wallet with the configured auto-payment amount
+        if ($wallet->balance < intval($request->balance * 100)) {
+            $mandate['amount'] = intval($request->amount * 100);
+        }
+
         $provider = PaymentProvider::factory($wallet);
 
-        $result = $provider->createMandate($wallet, $request);
+        $result = $provider->createMandate($wallet, $mandate);
 
         $result['status'] = 'success';
 
@@ -95,7 +82,7 @@
         $user = Auth::guard()->user();
 
         // TODO: Wallet selection
-        $wallet = $user->wallets->first();
+        $wallet = $user->wallets()->first();
 
         $provider = PaymentProvider::factory($wallet);
 
@@ -121,8 +108,43 @@
         $current_user = Auth::guard()->user();
 
         // TODO: Wallet selection
-        $wallet = $current_user->wallets->first();
+        $wallet = $current_user->wallets()->first();
+
+        // Input validation
+        if ($errors = self::mandateValidate($request, $wallet)) {
+            return response()->json(['status' => 'error', 'errors' => $errors], 422);
+        }
+
+        $wallet->setSettings([
+                'mandate_amount' => $request->amount,
+                'mandate_balance' => $request->balance,
+                // Re-enable the mandate to give it a chance to charge again
+                // after it has been disabled (e.g. because the mandate amount was too small)
+                'mandate_disabled' => null,
+        ]);
+
+        // Trigger auto-payment if the balance is below the threshold
+        if ($wallet->balance < intval($request->balance * 100)) {
+            \App\Jobs\WalletCharge::dispatch($wallet);
+        }
 
+        $result = self::walletMandate($wallet);
+        $result['status'] = 'success';
+        $result['message'] = \trans('app.mandate-update-success');
+
+        return response()->json($result);
+    }
+
+    /**
+     * Validate an auto-payment mandate request.
+     *
+     * @param \Illuminate\Http\Request $request The API request.
+     * @param \App\Wallet              $wallet  The wallet
+     *
+     * @return array|null List of errors on error or Null on success
+     */
+    protected static function mandateValidate(Request $request, Wallet $wallet)
+    {
         $rules = [
             'amount' => 'required|numeric',
             'balance' => 'required|numeric|min:0',
@@ -134,43 +156,27 @@
         // TODO: allow comma as a decimal point?
 
         if ($v->fails()) {
-            return response()->json(['status' => 'error', 'errors' => $v->errors()], 422);
+            return $v->errors();
         }
 
         $amount = (int) ($request->amount * 100);
 
         // Validate the minimum value
-        if ($amount < PaymentProvider::MIN_AMOUNT) {
-            $min = intval(PaymentProvider::MIN_AMOUNT / 100) . ' CHF';
-            $errors = ['amount' => \trans('validation.minamount', ['amount' => $min])];
-            return response()->json(['status' => 'error', 'errors' => $errors], 422);
+        // It has to be at least minimum payment amount and must cover current debt
+        if (
+            $wallet->balance < 0
+            && $wallet->balance * -1 > PaymentProvider::MIN_AMOUNT
+            && $wallet->balance + $amount < 0
+        ) {
+            return ['amount' => \trans('validation.minamountdebt')];
         }
 
-        // If the mandate is disabled the update will trigger
-        // an auto-payment and the amount must cover the debt
-        if ($wallet->getSetting('mandate_disabled')) {
-            if ($wallet->balance < 0 && $wallet->balance + $amount < 0) {
-                $errors = ['amount' => \trans('validation.minamountdebt')];
-                return response()->json(['status' => 'error', 'errors' => $errors], 422);
-            }
-
-            $wallet->setSetting('mandate_disabled', null);
-
-            if ($wallet->balance < intval($request->balance * 100)) {
-                \App\Jobs\WalletCharge::dispatch($wallet);
-            }
+        if ($amount < PaymentProvider::MIN_AMOUNT) {
+            $min = intval(PaymentProvider::MIN_AMOUNT / 100) . ' CHF';
+            return ['amount' => \trans('validation.minamount', ['amount' => $min])];
         }
 
-        $wallet->setSettings([
-                'mandate_amount' => $request->amount,
-                'mandate_balance' => $request->balance,
-        ]);
-
-        $result = self::walletMandate($wallet);
-        $result['status'] = 'success';
-        $result['message'] = \trans('app.mandate-update-success');
-
-        return response()->json($result);
+        return null;
     }
 
     /**
@@ -185,7 +191,7 @@
         $current_user = Auth::guard()->user();
 
         // TODO: Wallet selection
-        $wallet = $current_user->wallets->first();
+        $wallet = $current_user->wallets()->first();
 
         $rules = [
             'amount' => 'required|numeric',
diff --git a/src/app/Providers/Payment/Mollie.php b/src/app/Providers/Payment/Mollie.php
--- a/src/app/Providers/Payment/Mollie.php
+++ b/src/app/Providers/Payment/Mollie.php
@@ -37,7 +37,7 @@
      *
      * @param \App\Wallet $wallet  The wallet
      * @param array       $payment Payment data:
-     *                             - amount: Value in cents
+     *                             - amount: Value in cents (optional)
      *                             - currency: The operation currency
      *                             - description: Operation desc.
      *
@@ -50,10 +50,14 @@
         // Register the user in Mollie, if not yet done
         $customer_id = self::mollieCustomerId($wallet, true);
 
+        if (!isset($payment['amount'])) {
+            $payment['amount'] = 0;
+        }
+
         $request = [
             'amount' => [
                 'currency' => $payment['currency'],
-                'value' => '0.00',
+                'value' => sprintf('%.2f', $payment['amount'] / 100),
             ],
             'customerId' => $customer_id,
             'sequenceType' => 'first',
@@ -71,6 +75,13 @@
             $wallet->setSetting('mollie_mandate_id', $response->mandateId);
         }
 
+        // Store the payment reference in database
+        $payment['status'] = $response->status;
+        $payment['id'] = $response->id;
+        $payment['type'] = self::TYPE_MANDATE;
+
+        $this->storePayment($payment, $wallet->id);
+
         return [
             'id' => $response->id,
             'redirectUrl' => $response->getCheckoutUrl(),
diff --git a/src/app/Providers/Payment/Stripe.php b/src/app/Providers/Payment/Stripe.php
--- a/src/app/Providers/Payment/Stripe.php
+++ b/src/app/Providers/Payment/Stripe.php
@@ -56,7 +56,7 @@
      *
      * @param \App\Wallet $wallet  The wallet
      * @param array       $payment Payment data:
-     *                             - amount: Value in cents
+     *                             - amount: Value in cents (not used)
      *                             - currency: The operation currency
      *                             - description: Operation desc.
      *
@@ -77,12 +77,14 @@
             'mode' => 'setup',
         ];
 
+        // Note: Stripe does not allow to set amount for 'setup' operation
+        // We'll dispatch WalletCharge job when we receive a webhook request
+
         $session = StripeAPI\Checkout\Session::create($request);
 
-        $payment = [
-            'id' => $session->setup_intent,
-            'type' => self::TYPE_MANDATE,
-        ];
+        $payment['amount'] = 0;
+        $payment['id'] = $session->setup_intent;
+        $payment['type'] = self::TYPE_MANDATE;
 
         $this->storePayment($payment, $wallet->id);
 
@@ -355,6 +357,12 @@
 
                 if ($status == self::STATUS_PAID) {
                     $payment->wallet->setSetting('stripe_mandate_id', $intent->id);
+                    $threshold = intval($payment->wallet->getSetting('mandate_balance') * 100);
+
+                    // Top-up the wallet if balance is below the threshold
+                    if ($payment->wallet->balance < $threshold && $payment->status != self::STATUS_PAID) {
+                        \App\Jobs\WalletCharge::dispatch($payment->wallet);
+                    }
                 }
 
                 $payment->status = $status;
diff --git a/src/tests/Feature/Controller/PaymentsMollieTest.php b/src/tests/Feature/Controller/PaymentsMollieTest.php
--- a/src/tests/Feature/Controller/PaymentsMollieTest.php
+++ b/src/tests/Feature/Controller/PaymentsMollieTest.php
@@ -80,6 +80,7 @@
         $response->assertStatus(401);
 
         $user = $this->getTestUser('john@kolab.org');
+        $wallet = $user->wallets()->first();
 
         // Test creating a mandate (invalid input)
         $post = [];
@@ -104,7 +105,7 @@
         $this->assertCount(1, $json['errors']);
         $this->assertSame('The balance must be a number.', $json['errors']['balance'][0]);
 
-        // Test creating a mandate (invalid input)
+        // Test creating a mandate (amount smaller than the minimum value)
         $post = ['amount' => -100, 'balance' => 0];
         $response = $this->actingAs($user)->post("api/v4/payments/mandate", $post);
         $response->assertStatus(422);
@@ -116,6 +117,18 @@
         $min = intval(PaymentProvider::MIN_AMOUNT / 100) . ' CHF';
         $this->assertSame("Minimum amount for a single payment is {$min}.", $json['errors']['amount']);
 
+        // Test creating a mandate (negative balance, amount too small)
+        Wallet::where('id', $wallet->id)->update(['balance' => -2000]);
+        $post = ['amount' => PaymentProvider::MIN_AMOUNT / 100, 'balance' => 0];
+        $response = $this->actingAs($user)->post("api/v4/payments/mandate", $post);
+        $response->assertStatus(422);
+
+        $json = $response->json();
+
+        $this->assertSame('error', $json['status']);
+        $this->assertCount(1, $json['errors']);
+        $this->assertSame("The specified amount does not cover the balance on the account.", $json['errors']['amount']);
+
         // Test creating a mandate (valid input)
         $post = ['amount' => 20.10, 'balance' => 0];
         $response = $this->actingAs($user)->post("api/v4/payments/mandate", $post);
@@ -126,6 +139,13 @@
         $this->assertSame('success', $json['status']);
         $this->assertRegExp('|^https://www.mollie.com|', $json['redirectUrl']);
 
+        // Assert the proper payment amount has been used
+        $payment = Payment::where('id', $json['id'])->first();
+        $this->assertSame(2010, $payment->amount);
+        $this->assertSame($wallet->id, $payment->wallet_id);
+        $this->assertSame("Kolab Now Auto-Payment Setup", $payment->description);
+        $this->assertSame(PaymentProvider::TYPE_MANDATE, $payment->type);
+
         // Test fetching the mandate information
         $response = $this->actingAs($user)->get("api/v4/payments/mandate");
         $response->assertStatus(200);
@@ -176,6 +196,8 @@
 
         Bus::fake();
         $wallet->setSetting('mandate_disabled', null);
+        $wallet->balance = 1000;
+        $wallet->save();
 
         // Test updating mandate details (invalid input)
         $post = [];
@@ -202,7 +224,7 @@
         // Test updating a mandate (valid input)
         $responseStack->append(new Response(200, [], json_encode($mollie_response)));
 
-        $post = ['amount' => 30.10, 'balance' => 1];
+        $post = ['amount' => 30.10, 'balance' => 10];
         $response = $this->actingAs($user)->put("api/v4/payments/mandate", $post);
         $response->assertStatus(200);
 
@@ -216,7 +238,9 @@
         $wallet->refresh();
 
         $this->assertEquals(30.10, $wallet->getSetting('mandate_amount'));
-        $this->assertEquals(1, $wallet->getSetting('mandate_balance'));
+        $this->assertEquals(10, $wallet->getSetting('mandate_balance'));
+
+        Bus::assertDispatchedTimes(\App\Jobs\WalletCharge::class, 0);
 
         // Test updating a disabled mandate (invalid input)
         $wallet->setSetting('mandate_disabled', 1);
@@ -449,19 +473,24 @@
         $user = $this->getTestUser('john@kolab.org');
         $wallet = $user->wallets()->first();
 
-        // Create a valid mandate first
-        $this->createMandate($wallet, ['amount' => 20.10, 'balance' => 10]);
+        // Create a valid mandate first (balance=0, so there's no extra payment yet)
+        $this->createMandate($wallet, ['amount' => 20.10, 'balance' => 0]);
+
+        $wallet->setSetting('mandate_balance', 10);
 
         // Expect a recurring payment as we have a valid mandate at this point
+        // and the balance is below the threshold
         $result = PaymentsController::topUpWallet($wallet);
         $this->assertTrue($result);
 
-        // Check that the payments table contains a new record with proper amount
-        // There should be two records, one for the first payment and another for
-        // the recurring payment
-        $this->assertCount(1, $wallet->payments()->get());
-        $payment = $wallet->payments()->first();
-        $this->assertSame(2010, $payment->amount);
+        // Check that the payments table contains a new record with proper amount.
+        // There should be two records, one for the mandate payment and another for
+        // the top-up payment
+        $payments = $wallet->payments()->orderBy('amount')->get();
+        $this->assertCount(2, $payments);
+        $this->assertSame(0, $payments[0]->amount);
+        $this->assertSame(2010, $payments[1]->amount);
+        $payment = $payments[1];
 
         // In mollie we don't have to wait for a webhook, the response to
         // PaymentIntent already sets the status to 'paid', so we can test
@@ -488,7 +517,7 @@
         $wallet->setSetting('mandate_disabled', 1);
         $result = PaymentsController::topUpWallet($wallet);
         $this->assertFalse($result);
-        $this->assertCount(1, $wallet->payments()->get());
+        $this->assertCount(2, $wallet->payments()->get());
 
         // Expect no payment if balance is ok
         $wallet->setSetting('mandate_disabled', null);
@@ -496,7 +525,7 @@
         $wallet->save();
         $result = PaymentsController::topUpWallet($wallet);
         $this->assertFalse($result);
-        $this->assertCount(1, $wallet->payments()->get());
+        $this->assertCount(2, $wallet->payments()->get());
 
         // Expect no payment if the top-up amount is not enough
         $wallet->setSetting('mandate_disabled', null);
@@ -504,7 +533,7 @@
         $wallet->save();
         $result = PaymentsController::topUpWallet($wallet);
         $this->assertFalse($result);
-        $this->assertCount(1, $wallet->payments()->get());
+        $this->assertCount(2, $wallet->payments()->get());
 
         Bus::assertDispatchedTimes(\App\Jobs\PaymentMandateDisabledEmail::class, 1);
         Bus::assertDispatched(\App\Jobs\PaymentMandateDisabledEmail::class, function ($job) use ($wallet) {
@@ -518,7 +547,7 @@
         $wallet->save();
         $result = PaymentsController::topUpWallet($wallet);
         $this->assertFalse($result);
-        $this->assertCount(1, $wallet->payments()->get());
+        $this->assertCount(2, $wallet->payments()->get());
 
         Bus::assertDispatchedTimes(\App\Jobs\PaymentMandateDisabledEmail::class, 1);
 
diff --git a/src/tests/Feature/Controller/PaymentsStripeTest.php b/src/tests/Feature/Controller/PaymentsStripeTest.php
--- a/src/tests/Feature/Controller/PaymentsStripeTest.php
+++ b/src/tests/Feature/Controller/PaymentsStripeTest.php
@@ -72,6 +72,7 @@
         $response->assertStatus(401);
 
         $user = $this->getTestUser('john@kolab.org');
+        $wallet = $user->wallets()->first();
 
         // Test creating a mandate (invalid input)
         $post = [];
@@ -108,6 +109,18 @@
         $min = intval(PaymentProvider::MIN_AMOUNT / 100) . ' CHF';
         $this->assertSame("Minimum amount for a single payment is {$min}.", $json['errors']['amount']);
 
+        // Test creating a mandate (negative balance, amount too small)
+        Wallet::where('id', $wallet->id)->update(['balance' => -2000]);
+        $post = ['amount' => PaymentProvider::MIN_AMOUNT / 100, 'balance' => 0];
+        $response = $this->actingAs($user)->post("api/v4/payments/mandate", $post);
+        $response->assertStatus(422);
+
+        $json = $response->json();
+
+        $this->assertSame('error', $json['status']);
+        $this->assertCount(1, $json['errors']);
+        $this->assertSame("The specified amount does not cover the balance on the account.", $json['errors']['amount']);
+
         // Test creating a mandate (valid input)
         $post = ['amount' => 20.10, 'balance' => 0];
         $response = $this->actingAs($user)->post("api/v4/payments/mandate", $post);
@@ -118,6 +131,13 @@
         $this->assertSame('success', $json['status']);
         $this->assertRegExp('|^cs_test_|', $json['id']);
 
+        // Assert the proper payment amount has been used
+        // Stripe in 'setup' mode does not allow to set the amount
+        $payment = Payment::where('wallet_id', $wallet->id)->first();
+        $this->assertSame(0, $payment->amount);
+        $this->assertSame("Kolab Now Auto-Payment Setup", $payment->description);
+        $this->assertSame(PaymentProvider::TYPE_MANDATE, $payment->type);
+
         // Test fetching the mandate information
         $response = $this->actingAs($user)->get("api/v4/payments/mandate");
         $response->assertStatus(200);
@@ -176,6 +196,8 @@
 
         // Test updating mandate details (invalid input)
         $wallet->setSetting('mandate_disabled', null);
+        $wallet->balance = 1000;
+        $wallet->save();
         $user->refresh();
         $post = [];
         $response = $this->actingAs($user)->put("api/v4/payments/mandate", $post);
@@ -202,7 +224,7 @@
         $client->addResponse($setupIntent);
         $client->addResponse($paymentMethod);
 
-        $post = ['amount' => 30.10, 'balance' => 1];
+        $post = ['amount' => 30.10, 'balance' => 10];
         $response = $this->actingAs($user)->put("api/v4/payments/mandate", $post);
         $response->assertStatus(200);
 
@@ -211,7 +233,7 @@
         $this->assertSame('success', $json['status']);
         $this->assertSame('The auto-payment has been updated.', $json['message']);
         $this->assertEquals(30.10, $wallet->getSetting('mandate_amount'));
-        $this->assertEquals(1, $wallet->getSetting('mandate_balance'));
+        $this->assertEquals(10, $wallet->getSetting('mandate_balance'));
         $this->assertSame('AAA', $json['id']);
         $this->assertFalse($json['isDisabled']);
 
@@ -406,6 +428,7 @@
     {
         $user = $this->getTestUser('john@kolab.org');
         $wallet = $user->wallets()->first();
+        Wallet::where('id', $wallet->id)->update(['balance' => -1000]);
 
         // Test creating a mandate (valid input)
         $post = ['amount' => 20.10, 'balance' => 0];
@@ -438,6 +461,8 @@
             'type' => "setup_intent.succeeded"
         ];
 
+        Bus::fake();
+
         // Test payment succeeded event
         $response = $this->webhookRequest($post);
         $response->assertStatus(200);
@@ -447,6 +472,13 @@
         $this->assertSame(PaymentProvider::STATUS_PAID, $payment->status);
         $this->assertSame($payment->id, $wallet->fresh()->getSetting('stripe_mandate_id'));
 
+        // Expect a WalletCharge job if the balance is negative
+        Bus::assertDispatchedTimes(\App\Jobs\WalletCharge::class, 1);
+        Bus::assertDispatched(\App\Jobs\WalletCharge::class, function ($job) use ($wallet) {
+            $job_wallet = TestCase::getObjectProperty($job, 'wallet');
+            return $job_wallet->id === $wallet->id;
+        });
+
         // TODO: test other setup_intent.* events
     }
 
diff --git a/src/tests/Feature/Controller/WalletsTest.php b/src/tests/Feature/Controller/WalletsTest.php
--- a/src/tests/Feature/Controller/WalletsTest.php
+++ b/src/tests/Feature/Controller/WalletsTest.php
@@ -190,6 +190,8 @@
         $john = $this->getTestUser('john@kolab.org');
         $jack = $this->getTestUser('jack@kolab.org');
         $wallet = $john->wallets()->first();
+        $wallet->balance = -100;
+        $wallet->save();
 
         // Accessing a wallet of someone else
         $response = $this->actingAs($jack)->get("api/v4/wallets/{$wallet->id}");
@@ -209,7 +211,6 @@
         $this->assertSame('CHF', $json['currency']);
         $this->assertSame($wallet->balance, $json['balance']);
         $this->assertTrue(empty($json['description']));
-        // TODO: This assertion does not work after a longer while from seeding
         $this->assertTrue(!empty($json['notice']));
     }