mark a invoice as unpayable

I’am looking for a way to mark a invoice as unpayable. I have a few customers that will not be finishing their payments on their invoices

Do you mean unpayable by the client? If you delete the client record they can no longer access the invoices.

Something like that…
in the bookkeeping must be marked like the amount of the invoice was not received.

In that case deleting the client won’t work as the invoices won’t be shown. It sounds like you may want to be using a separate accounting application, we just handle invoices not full accounting.

in this case i think will suit me better to be able to permanently delete that invoice and add another one with that number.

Do you plan to add the “permanently delete the invoice” from the system ?

In order to retain referential integrity we don’t plan to add permanent deletion.

You’d need to change the invoice number of the original invoice to something else to create a new invoice with that number.