Generating payment receipts and invoices with a balance of $0

Several users have requested the addition of a feature that allows for the generation of official receipts once the customer has completed payment. It would also be necessary to be able to enter the amount of a received deposit directly on the invoice to display the remaining balance due, and ultimately to issue a paid invoice showing a balance of $0. This would prevent users from having to rely on external accounting software (such as QuickBooks or Acomba) to provide this proof of payment.