Don't allow deletion of an uploaded payment order + allow to cancel an uploaded payment order

account_payment_order/models/account_payment_order.py

@@ -95,6 +95,14 @@ class AccountPaymentOrder(models.Model):
         'account.move', 'payment_order_id', string='Journal Entries',
         readonly=True)
 
+    @api.multi
+    def unlink(self):
+        for order in self:
+            if order.state == 'uploaded':
+                raise ValidationError(_(
+                    "You cannot delete an uploaded payment order. You can "
+                    "cancel it in order to do so."))
+
     @api.multi
     @api.constrains('payment_type', 'payment_mode_id')
     def payment_order_constraints(self):
@@ -175,6 +183,16 @@ class AccountPaymentOrder(models.Model):
             })
         return True
 
+    @api.multi
+    def action_done_cancel(self):
+        for move in self.move_ids:
+            move.button_cancel()
+            for move_line in move.line_ids:
+                move_line.remove_move_reconcile()
+            move.unlink()
+        self.action_cancel()
+        return True
+
     @api.multi
     def cancel2draft(self):
         self.write({'state': 'draft'})

account_payment_order/views/account_payment_order.xml

@@ -22,6 +22,8 @@
                     string="Back to Draft" />
                 <button name="action_cancel" type="object" states="draft,open,generated"
                     string="Cancel Payments"/>
+                <button name="action_done_cancel" type="object" states="uploaded"
+                    string="Cancel Payments"/>
                 <field name="state" widget="statusbar"/>
             </header>
             <sheet>