Voiding (Reversing) a payment to a vendor reverse the general ledger postings related to the initial payment, create a "reverse" entry in Bank Register, and will reinstate the vendor invoices and credits to a status making them available to be re-paid.
1) Go to Transactions - Accounts Payable - Pay A Vendor
2) Select "Open" and input part of the vendor's name to search for prior payments.
3) In the lists of records returned, insure you have Payment Date and Reference fields in the grid. You may sort by either column to make it easier to locate the desired payment.
4) Select the payment. You will be presented with message "The payment has already been posted". Simply click "OK"
5) From the Actions menu, chose either "Reverse This Payment" or "Reverse This Payment in Another Period".