Can I use the writeoff function in a/r to move an o/s balance in a/r to be applied and reduce the payment of an invoice in a/p for the same vendor?

If not is there another way to do in beside adjusting a/r and then entering credit in a/p?

Thanks

Not quite.

You can use the writeoff function in AR to write off a customer credit, and at the same time issue a manual check in AP to pay the customer, but not the other way around.

The alternative is the way you suggest, just make sure to use the same GL account for both adjustments.

Steve