Due to the age of the invoice, this should not be reversed. Instead, follow the steps below to remove the invoice from your creditor listings:
From the DPS Home Screen, select Purchase Ledger.
Select Pay Supplier.
Pick up and pay the invoice you wish to remove, marking this as a Firm Payment.
Still in the Supplier payment screen re-enter the details from the previous posting, but select Firm Refunds.
The items will then contra on your bank reconciliation and clear your creditor listings.