To prepare your company file for a new financial year you need to perform the Start A New Financial Year procedure. When this procedure is run, you need to retain unpaid payment details to be able to process payments for transactions recorded in a prior financial year.

During the procedure the Receipts & Payments to be Processed window appears.

Select the Keep Disbursements Grouped with Electronic Payments option (it should be selected by default). Unpaid payment details are now retained for later processing.