Manual invoice checking often works well when a business is small and transaction volumes are predictable. A small accounts team checking invoices visually may approve dozens of minor weight or volumetric adjustments because each seems plausible individually. Manual checking is particularly weak at distinguishing a legitimate recurring cost from a recurring problem. Final ThoughtsThe weakness of manual invoice checking is not that accounts staff are careless. Weight corrections, volumetric adjustments and later billing changes can all look perfectly ordinary on an invoice.