If the supplier has been invoiced and has been overpaid, then his debit appears on the statement (Test Supplier (£)), but if he has been paid prior to invoicing or it has opening balance at the beginning of the period, it is not being show on Aged Payables statement:
This subject has been raised before. It reveals differences of opinion among various users, accountants, and the developer over what should appear on aging reports. Some believe aging reports should match Accounts receivable/payable. Others believe aging reports should only show aging of invoices, because payments cannot be aged, by definition.
If you search the internet, you can find support for and application of both opinions. This really comes down to what the report designer intends to show. Obviously, Manager’s developer (as of now) favors showing only the invoices. This emphasizes payment/collection performance. And remember, the aging reports are not the accounts; they are only reports with certain content, in this case only about invoices.
The current approach makes sense given the approach taken to recording customer and supplier credits. Some accountants prefer those to be visible in separate accounts, rather than netting them out in Accounts receivable/payable. In that situation, the argument for having aging reports match Accounts receivable/payable would be stronger. When credits are combined with what is owed, as they currently are in Manager, a large deposit or credit could obscure late payment performance.