If a business gives you your change in counterfeit money, you’re probably out of luck unless you can prove it right there on the spot. But what if the fake money comes from an arm of the federal government?

Los Angeles Times business columnist David Lazarus tells the story of an L.A. resident who went to the post office with a postal service money order for $1,000, cashed it and went to use some of that money at a gas station. The clerk identified a $100 bill as a counterfeit and called the police, who came to the station and discovered the bills were actually $5 bills that had been bleached. Neither the police nor the gas station attendant could do anything but refer the payer to the Secret Service.

Lazarus advises contacting the Secret Service right away if you feel you’ve received questionable bills.