When ready click Pay. The Pay Invoice dialog opens.
From the Pay Invoice dialog:
Enter the date the invoice was paid in the Date Paid field. This date does not need to be the same as the date the invoice payment status changes to Paid and allows you to indicate when payment was submitted to the vendor, rather than when the invoice was marked as paid in Acquisitions.
(Optional) Enter a Payment Reference ID. A payment reference ID is a check or transaction number for the payment actually submitted for this invoice.
(Optional) Enter an External Invoice ID. An external invoice ID is a unique identifier for the invoice used by an external financial system (e.g. such as the campus financial system).
Click Pay.
(Optional) See Unpay an invoice when making corrections after payment.