Buying imitation currency online is legal. Passing it off as real is illegal, but in Washington, it’s happened several times over the past two weeks.

Washington Police Department has received several reports of counterfeit money being used to purchase items from local stores — in three cases, the person using a bill successfully passed it off as legitimate, according to law enforcement officials. In another incident, a cashier at Mom’s Grill on John Small Avenue recognized that a bill was not real and reported the incident to police.

While some counterfeit bills are near indistinguishable from real currency, those recently passed off in Washington have a feature in common: on the back of the bill, in the location where “The United States of America” is usually printed, are the words “Motion Picture Use Only.” It’s fake money made for film purposes, but with only a cursory glance during a transaction, it could pass for real.

According to Washington Police and Fire Services Director Stacy Drakeford, those who deal with money should be eyeing it carefully.

Outside of the obvious written description on money intended for use as a prop, there are other ways to tell if a bill is real or fake.

“There are things to look for that are anti-counterfeit measures,” said Lt. William Chrismon, spokesman for the Washington Police Department.

Chrismon said those things to look for include: microprinting — fine lines and fine printing on the bill that makes it difficult to duplicate; watermarks that can be seen when held up to the light — a $20 bill will show a duplication of Andrew Jackson’s face in the lower right corner; color-shifting inks that will change color as the bill is tilted; a thread of text running vertically down the bill declaring the banknote’s denomination, which can also be seen when held to the light; and raised printing which gives a note’s surface a distinctive texture.

Those who find themselves in possession of counterfeit bills are asked to notify police and make sure it’s taken out of circulation, according to authorities.