diff --git a/addons/account/models/account_invoice.py b/addons/account/models/account_invoice.py
index b7a885ef53e..f036e997b44 100644
--- a/addons/account/models/account_invoice.py
+++ b/addons/account/models/account_invoice.py
@@ -103,7 +103,7 @@ class AccountInvoice(models.Model):
     def _compute_residual(self):
         residual = 0.0
         residual_company_signed = 0.0
-        sign = self.type in ['in_refund', 'out_refund'] and -1 or 1
+        sign = self.type in ['in_invoice', 'out_refund'] and -1 or 1
         for line in self.sudo().move_id.line_ids:
             if line.account_id == self.account_id:
                 residual_company_signed += line.amount_residual
diff --git a/addons/account/models/account_payment.py b/addons/account/models/account_payment.py
index 7d1231ece2e..398982ec836 100644
--- a/addons/account/models/account_payment.py
+++ b/addons/account/models/account_payment.py
@@ -118,11 +118,11 @@ class account_register_payments(models.TransientModel):
         total = 0
         for inv in invoice_ids:
             if inv.currency_id == payment_currency:
-                total += MAP_INVOICE_TYPE_PAYMENT_SIGN[inv.type] * inv.residual_signed
+                total += inv.residual_signed
             else:
                 amount_residual = inv.company_currency_id.with_context(date=self.payment_date).compute(
                     inv.residual_company_signed, payment_currency)
-                total += MAP_INVOICE_TYPE_PAYMENT_SIGN[inv.type] * amount_residual
+                total += amount_residual
         return total
 
     @api.onchange('journal_id')
@@ -569,8 +569,9 @@ class account_payment(models.Model):
             # to avoid loss of precision during the currency rate computations. See revision 20935462a0cabeb45480ce70114ff2f4e91eaf79 for a detailed example.
             total_residual_company_signed = sum(invoice.residual_company_signed for invoice in self.invoice_ids)
             total_payment_company_signed = self.currency_id.with_context(date=self.payment_date).compute(self.amount, self.company_id.currency_id)
+            # amout_wo must be positive for out_invoice and in_refund and negative for in_invoice and out_refund in standard use case
             if self.invoice_ids[0].type in ['in_invoice', 'out_refund']:
-                amount_wo = total_payment_company_signed - total_residual_company_signed
+                amount_wo = total_payment_company_signed + total_residual_company_signed
             else:
                 amount_wo = total_residual_company_signed - total_payment_company_signed
             # Align the sign of the secondary currency writeoff amount with the sign of the writeoff
diff --git a/addons/account/tests/test_payment.py b/addons/account/tests/test_payment.py
index 9855452e209..8f671f957c9 100644
--- a/addons/account/tests/test_payment.py
+++ b/addons/account/tests/test_payment.py
@@ -370,3 +370,29 @@ class TestPayment(AccountingTestCase):
             {'account_id': self.account_payable.id, 'debit': 0.0, 'credit': 8.65, 'amount_currency': -13.22, 'currency_id': self.currency_usd_id},
             {'account_id': self.account_receivable.id, 'debit': 0.0, 'credit': 7.7, 'amount_currency': -11.78, 'currency_id': self.currency_usd_id},
         ])
+
+    def test_payment_and_writeoff_out_refund(self):
+        # Use case:
+        # Company is in EUR, create a credit note for 100 EUR and register payment of 90.
+        # Mark invoice as fully paid with a write_off
+        # Check that all the aml are correctly created.
+        invoice = self.create_invoice(amount=100, type='out_refund', currency_id=self.currency_eur_id, partner=self.partner_agrolait.id)
+        # register payment on invoice
+        payment = self.payment_model.create({'payment_type': 'outbound',
+            'payment_method_id': self.env.ref('account.account_payment_method_manual_in').id,
+            'partner_type': 'customer',
+            'partner_id': self.partner_agrolait.id,
+            'amount': 90,
+            'payment_date': time.strftime('%Y') + '-07-15',
+            'payment_difference_handling': 'reconcile',
+            'writeoff_account_id': self.account_payable.id,
+            'journal_id': self.bank_journal_euro.id,
+            'invoice_ids': [(4, invoice.id, None)]
+            })
+        payment.post()
+        self.check_journal_items(payment.move_line_ids, [
+            {'account_id': self.account_eur.id, 'debit': 0.0, 'credit': 90.0, 'amount_currency': 0.0, 'currency_id': False},
+            {'account_id': self.account_payable.id, 'debit': 0.0, 'credit': 10.0, 'amount_currency': 0.0, 'currency_id': False},
+            {'account_id': self.account_receivable.id, 'debit': 100.0, 'credit': 0.0, 'amount_currency': 0.0, 'currency_id': False},
+        ])
+        self.assertEqual(invoice.state, 'paid')