Hi all, Does anyone know of the official and legal method under commercial law to add a late payment fee to an invoice? I am a sole trader and freelance worker. I'm unsure whether to create a new invoice number, or alter the current invoice and add an "R" for revised to the original invoice number. Do I change the issue date, and do I create a new due date? Is there a general guideon what percentage of a fee should be added, after what period of time? Many thanks!