existence of TPs bal

Existence of assets/liabilities - you start with FS and work backwards: FS -> TB -> Payables control a/c balance reconciled to list of individual balances -> make-up of individual balances -> purchase invoices -> GRNs. The GRN confirms the liability to the supplier was incurred (existence) - there is no need to trace back further to purchase order/requisition (which don't in any case confirm the liability). You can't agree balances directly to GRNs (or GDNs) because balances are monetary amounts ($).

You wrote ... "a sample of trade payabels balances ($$$$s), agree it to its GRN" I am saying this is NOT POSSIBLE - for any of the following reasons: (1) You cannot agree something that is $s to something that is not $s (2) LOOK at Chapter 13 - note the main activities in the purchase system ... only the invoice tells you how much the liability is - the payment amount will be the invoice amount (3) THINK (assumed knowledge of FA) - how do you get a payables balance? Dr Purchases Cr Payable The INVOICE amount as recorded in the purchase day book (a book of prime entry). (4) GRNs are NOT recorded in a book of prime entry so cannot be "found", "identified" directly from the payables account - only INDIRECTLY via the invoice that is recorded in the payables a/c