It is possible to create a "Retrospective" Aged Creditors Report within Sage 200, but the output is not always what is expected.
BOTH the "Transaction Payment Date" AND the "Payment Allocation Date" must be beyond the "Ageing Date", otherwise those transactions will be excluded from the report. This will cause a difference between the report total and the values within the Nominal Ledger.
These transaction dates are set within the Payment Processing routines, but essentially the allocation date defaults to the date at which the payment routine is physically run. Best practices suggest that the "Payment Date" AND the "Allocation Date" be kept within the SAME processing month. The simplest way to do this would be to run the payment routine during the same month as the intended payment date.