Anchorage Police are warning merchants to be careful about counterfeit bills that have been circulating in town since late summer. Some business owners have seen counterfeits recently and say they're getting fed-up with the fakes.

Cindy Speer, co-owner of Big Mike's Tesoro on Jewel Lake Road has a collection of counterfeit money that she keeps as a training tool for employees. She said she got her latest bad bill on Tuesday when a woman tried to pass a $100 bill that was obviously fake.

"It wasn't even the right size," said Speer. "It was horrible!"

Speer said her clerk caught the bill right away and refused to give it back. The store is required to confiscate counterfeit cash under federal law, which can sometimes lead to a confrontation.

"Most of them aren't happy you aren't giving it back," said Speer. "[This woman] was insistent, she wanted it back. But I'm not giving it back so she can try it on somebody else."

Counterfeit bills aren't just a problem for merchants, they're also a problem for banks.

"In 2017, we've seen an uptick more than any other year before," said Wells Fargo Branch manager Shelby Allen.

Allen said banks and businesses have tools to use that can tell when a bill is fake.

From a special marker that makes a dark line on a bill that isn't real, to a sophisticated UV light box that can reveal hidden markings.

But Allen said some bills have issues anyone can spot. The ink on counterfeit bills will sometimes be darker and the the paper will have a flat, almost oily feel. Newer bills may also have holograms you can see when you hold them up to the light. Allen said it can pay to look.

"Whenever you are getting change back, you can tell just by holding the bills in your hand a lot of times," said Allen. "If you have a fraudulent bill in there, ask (the clerk) to switch it out for you."

Police said merchants who receive counterfeit bills should report the crime. They can file a report online at the Muni website, but they also need to call the non-emergency number for Dispatch at 786-8900 and ask for an officer to respond. Police say they need to collect the bad bills for evidence.