diff --git a/addons/account/models/account_payment.py b/addons/account/models/account_payment.py
index d1c0de1dc71..fa0470265ed 100644
--- a/addons/account/models/account_payment.py
+++ b/addons/account/models/account_payment.py
@@ -181,11 +181,13 @@ class AccountPayment(models.Model):
         if self.payment_type == 'inbound':
             # Receive money.
             counterpart_amount = -self.amount
+            write_off_amount *= -1
         elif self.payment_type == 'outbound':
             # Send money.
             counterpart_amount = self.amount
         else:
             counterpart_amount = 0.0
+            write_off_amount = 0.0
 
         # Manage currency.
         if self.currency_id == self.company_id.currency_id:
diff --git a/addons/account/tests/test_account_payment_register.py b/addons/account/tests/test_account_payment_register.py
index af142f72b5a..ba6e6c6c63c 100644
--- a/addons/account/tests/test_account_payment_register.py
+++ b/addons/account/tests/test_account_payment_register.py
@@ -153,7 +153,7 @@ class TestAccountPaymentRegister(AccountTestInvoicingCommon):
             },
         ])
 
-    def test_register_payment_single_batch_grouped_writeoff_lower_amount(self):
+    def test_register_payment_single_batch_grouped_writeoff_lower_amount_debit(self):
         ''' Pay 800.0 with 'reconcile' as payment difference handling on two customer invoices (1000 + 2000). '''
         active_ids = (self.out_invoice_1 + self.out_invoice_2).ids
         payments = self.env['account.payment.register'].with_context(active_model='account.move', active_ids=active_ids).create({
@@ -162,7 +162,6 @@ class TestAccountPaymentRegister(AccountTestInvoicingCommon):
             'payment_difference_handling': 'reconcile',
             'writeoff_account_id': self.company_data['default_account_revenue'].id,
             'writeoff_label': 'writeoff',
-            'currency_id': self.currency_data['currency'].id,
             'payment_method_id': self.custom_payment_method_in.id,
         })._create_payments()
 
@@ -196,7 +195,7 @@ class TestAccountPaymentRegister(AccountTestInvoicingCommon):
             },
         ])
 
-    def test_register_payment_single_batch_grouped_writeoff_higher_amount(self):
+    def test_register_payment_single_batch_grouped_writeoff_higher_amount_debit(self):
         ''' Pay 3100.0 with 'reconcile' as payment difference handling on two customer invoices (1000 + 2000). '''
         active_ids = (self.out_invoice_1 + self.out_invoice_2).ids
         payments = self.env['account.payment.register'].with_context(active_model='account.move', active_ids=active_ids).create({
@@ -205,7 +204,6 @@ class TestAccountPaymentRegister(AccountTestInvoicingCommon):
             'payment_difference_handling': 'reconcile',
             'writeoff_account_id': self.company_data['default_account_revenue'].id,
             'writeoff_label': 'writeoff',
-            'currency_id': self.currency_data['currency'].id,
             'payment_method_id': self.custom_payment_method_in.id,
         })._create_payments()
 
@@ -239,6 +237,90 @@ class TestAccountPaymentRegister(AccountTestInvoicingCommon):
             },
         ])
 
+    def test_register_payment_single_batch_grouped_writeoff_lower_amount_credit(self):
+        ''' Pay 800.0 with 'reconcile' as payment difference handling on two vendor billes (1000 + 2000). '''
+        active_ids = (self.in_invoice_1 + self.in_invoice_2).ids
+        payments = self.env['account.payment.register'].with_context(active_model='account.move', active_ids=active_ids).create({
+            'amount': 800.0,
+            'group_payment': True,
+            'payment_difference_handling': 'reconcile',
+            'writeoff_account_id': self.company_data['default_account_revenue'].id,
+            'writeoff_label': 'writeoff',
+            'payment_method_id': self.custom_payment_method_in.id,
+        })._create_payments()
+
+        self.assertRecordValues(payments, [{
+            'payment_method_id': self.custom_payment_method_in.id,
+        }])
+        self.assertRecordValues(payments.line_ids.sorted('balance'), [
+            # Writeoff line:
+            {
+                'debit': 0.0,
+                'credit': 2200.0,
+                'currency_id': False,
+                'amount_currency': 0.0,
+                'reconciled': False,
+            },
+            # Liquidity line:
+            {
+                'debit': 0.0,
+                'credit': 800.0,
+                'currency_id': False,
+                'amount_currency': 0.0,
+                'reconciled': False,
+            },
+            # Payable line:
+            {
+                'debit': 3000.0,
+                'credit': 0.0,
+                'currency_id': False,
+                'amount_currency': 0.0,
+                'reconciled': True,
+            },
+        ])
+
+    def test_register_payment_single_batch_grouped_writeoff_higher_amount_credit(self):
+        ''' Pay 3100.0 with 'reconcile' as payment difference handling on two vendor billes (1000 + 2000). '''
+        active_ids = (self.in_invoice_1 + self.in_invoice_2).ids
+        payments = self.env['account.payment.register'].with_context(active_model='account.move', active_ids=active_ids).create({
+            'amount': 3100.0,
+            'group_payment': True,
+            'payment_difference_handling': 'reconcile',
+            'writeoff_account_id': self.company_data['default_account_revenue'].id,
+            'writeoff_label': 'writeoff',
+            'payment_method_id': self.custom_payment_method_in.id,
+        })._create_payments()
+
+        self.assertRecordValues(payments, [{
+            'payment_method_id': self.custom_payment_method_in.id,
+        }])
+        self.assertRecordValues(payments.line_ids.sorted('balance'), [
+            # Liquidity line:
+            {
+                'debit': 0.0,
+                'credit': 3100.0,
+                'currency_id': False,
+                'amount_currency': 0.0,
+                'reconciled': False,
+            },
+            # Writeoff line:
+            {
+                'debit': 100.0,
+                'credit': 0.0,
+                'currency_id': False,
+                'amount_currency': 0.0,
+                'reconciled': False,
+            },
+            # Payable line:
+            {
+                'debit': 3000.0,
+                'credit': 0.0,
+                'currency_id': False,
+                'amount_currency': 0.0,
+                'reconciled': True,
+            },
+        ])
+
     def test_register_payment_single_batch_not_grouped(self):
         ''' Choose to pay two customer invoices with separated payments (1000 + 2000). '''
         active_ids = (self.out_invoice_1 + self.out_invoice_2).ids
diff --git a/addons/account/wizard/account_payment_register.py b/addons/account/wizard/account_payment_register.py
index c36f5bbfb9c..a4a6fdca2a4 100644
--- a/addons/account/wizard/account_payment_register.py
+++ b/addons/account/wizard/account_payment_register.py
@@ -419,7 +419,7 @@ class AccountPaymentRegister(models.TransientModel):
         if self.payment_difference and self.payment_difference_handling == 'reconcile':
             payment_vals['write_off_line_vals'] = {
                 'name': self.writeoff_label,
-                'amount': -self.payment_difference,
+                'amount': self.payment_difference,
                 'account_id': self.writeoff_account_id.id,
             }
         return payment_vals