A vendor's invoice doesn't add up and you can mention the client or auditor who will eventually review those costs.

When Twango pads Cugel's account with illegible invoices, Cugel only wonders aloud, "from sheer idle curiosity, shall I put the question to Master Soldinck?" — and the "misplaced decimal" turns up at once. The threat of inspection does the work; the leverage is borrowed and never spent.