OLD Invoice Numbers or gaps being used out of sequence if user manually changes a date.

Hi nduro 

Thanks for your feedback. I have passed this on to the team. In the meantime the invoice numbering will continue to work like this. The Invoice No. field shows the next available number for your invoices, quotes and orders. If you click the Invoice No. field, Auto # appears to confirm that the number has been automatically selected for you. When you type a different number, subsequent invoice numbers will then increment from the new number. This is not something that can be changed at the moment.