When copying an older invoice to a new invoice - eg an old Purchase Invoice to a new Purchase Invoice, it does not update the due date field to use the new purchase invoice form defaults. So an old invoice using Due Date by does not update to due Date Net. My understanding is that the Copy to feature should reset all date related aspects, whereas the Clone should be an identical clone.
I want new invoices to use the Due Date Net and 14 days, not Due Date By which was historically blank. This way I can get rid of the problem where invoices show as overdue the very next day as historically I never set a due date on past invoices. So I have addressed this in form defaults for invoices.
However, this does not address historical invoices that are being copied.