Received Not Invoiced (GRNI Aging)

The GRNI working surface (§4.5), present when GRNI is on: every goods receipt still waiting for its purchase invoice, aged by how long it has waited, and totalling exactly the received-not-invoiced liability in the books — if the report and the account ever disagreed, something would be wrong by construction. Its use is operational: work the oldest rows. Each one is either an invoice that has not been entered (enter it), an invoice that never arrived (chase the supplier), or a receipt that should not stand (investigate it). A healthy balance is young and small.