Due date is calculating in accounting documents based on billing date and in invoice it is calculating based on posting date There is a invoice for which billing was created on 31.08.2018 The accounting document got posted on 12.09.2018 Doc date 31.08.2018 Posting date 12.09.2018 Due date while displaying ACC doc-30.10.2018 Payterms -60 days But In invoice due date is 11.11.2018 The due date in accounting doc is 30.10.2018 which is based on billing date 31.08.2018 The due date on invoice is 11.11.2018 which is based on posting /creation date 12.09.2018