I have a case where draft invoice is created but the final invoice amount is not known until a later date, but the advance has to be paid upfront.

If I use a voucher to make the advance payment, how do I link it to the invoice later on when the invoice is validated? I tried partial reconcile but that brought in a lot of unrelated items in the payment grid.

Is there a programmatic way to do this?

If not, what are the implications of the following approach: validate the invoice, make the payment, afterwards when the final invoice amount is known, modify the account moves (journal items) programmatically...??

Thanks