The three failures approvals are meant to catch
First, duplicates. A supplier emails the invoice, then sends a reminder with the same invoice attached, then the courier drops a paper copy at reception. Three documents, one debt. Second, price drift: the agreed rate for site labour was AED 18 an hour and the March invoice says AED 21. Third, broken tax documents, where a bill shows 5% VAT but no supplier TRN, so the input tax may not be recoverable when your accountant checks it.
Most companies try to catch these with a manager's signature. A manager signing forty bills on a Thursday afternoon catches very little. The fix is to put the checking before the signing.