You can modify or delete unposted Accounts Payable transactions in the New A/P Transactions window. Once a transaction has been posted, you can modify a limited amount of information about that transaction in the AP Invoice Maintenance and Payment window. Otherwise, you must create an offsetting transaction to change the original transaction. For example, to modify the distributions to General Ledger that were made at the time the transaction was posted, you must create an "adjustment voucher". Similarly, to delete a posted transaction, you must create a "cancellation voucher" to back out the original transaction.
You can also display transaction information for both posted and unposted transactions. Unposted transactions can be viewed in the New A/P Transactions window, while posted transactions can be viewed in the View Posted A/P Transactions window.