Log in to https://buyers.mpuk.basware.com/admin/login/auth and go to Supplier Portal:
When in Supplier Portal, go to Admin – Company Admin on the right hand side
Scroll down until you see the invoice section on the right side of the screen and untick the ‘Automatic numbering’:
Once this has been unticked, scroll to the top of the screen, and click save on the top right using the button.
Log out and back in, the changes will have taken affect and you will now be prompted to input an invoice number when creating an invoice before being able to save the invoice draft.