We have come across a scenario where a client had edited a final invoice. This is usually accepted within Commusoft, however, in these cases, the 'Save' button was not clickable. This invoice was sent to their accounting package. This was not the problem either because Commusoft will prompt you to edit this in your accounting package too.
The type of edit, in this case, caused the issue. The client had edited the breakdown type and in this case, it is not possible to complete this action after it has been sent to an accounting package. Please credit the invoice, and create a new invoice in the correct breakdown you require.