A customer of mine missed an old invoice on a recent payment. We offer a 2% 10 NET 30 discount which they took on the two that they paid. Missing an invoice is not uncommon so I shot them an e-mail reminder asking if they needed a copy of the missed invoice. Their response was shocking in it's brutal honesty
"We have the invoice. We just missed the 10 day discount window so we will pay the first Friday after 45 days."
Customers play games all the time to scam a discount, but I've never had one admit it before.