Agree with Peter O'Kool comment to email invoice: "Not only email it, also with payment method (discrete) description and the word 'PAID'.
example: PAID, C.Card ending 9999, or bank acct ending 1111 or whatever is secure to do. Also in PDF format for saving it, with a common-sense name like INVOICE4444010118 (invoice # and date)."
Agree with Peter O'Kool comment to email invoice: "Not only email it, also with payment method (discrete) description and the word 'PAID'.
example: PAID, C.Card ending 9999, or bank acct ending 1111 or whatever is secure to do. Also in PDF format for saving it, with a common-sense name like INVOICE4444010118 (invoice # and date)."