Issue - Install 'Accounting' module - Create a new 'Tax' X with a fixed price (e.g.: O.O57 $) - Create a new 'Customer Invoice' - Add a product P and set unit price to 0 $ - Set tax X to product P Total tax amount : - 0.06 $ . Solution The sign must be forced to a negative sign in case the balance is on credit to avoid negatif taxes amount. enterprise PR : https://github.com/odoo/enterprise/pull/15035 opw-2378978 closes odoo/odoo#62758 X-original-commit: 684855529e8aaafa0cb90f958d19c563d6e2a897 Related: odoo/enterprise#15105 Signed-off-by: Laurent Smet <smetl@users.noreply.github.com> Signed-off-by: bon-odoo <nboulif@users.noreply.github.com>