MIAMI (CBSMiami) – Thanksgiving isn’t just about turkey, it’s about shopping of course, but South Florida retailers are keeping an alert eye on customers who try to pay with counterfeit cash.

According to the Sun Sentinel, South Florida is known as one of the nation’s leaders in counterfeit cash and the U.S. Secret Service counterfeit division in Miami has already confiscated nearly $85,000 in counterfeit currency.

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Ron Remer, with the U.S. Secret Service, told the Sentinel they see a spike in late November and it lasts through the holidays.

South Florida ranks among the top metro areas in the country for trafficking counterfeit notes, behind New York, Los Angeles and Chicago, Remer said.

Law enforcement tracks $60,000 to $80,000 a week in counterfeit bills in Miami-Dade, Broward and Monroe counties, Remer said.

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He said most counterfeit bills in South Florida are real bills that are bleached and reprinted to look like larger denominations.

The bleached bills pass the ‘pen test’ so retailers need to also look at the watermark on the bills. The watermarks can be seen by holding a bill up to a light. If you see Abraham Lincoln on a $100 bill, then there’s a problem. Lincoln is on a $5 bill; Benjamin Franklin is on a $100.

Secret Service agents have been training retail employees at malls across South Florida this week in preparation for the busy holiday season.

One common trick in South Florida is to use counterfeit money to buy an expensive item like a computer, and then return it for real currency at another location of the same retailer.

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Shoppers who think they’ve been given a counterfeit bill should call the U.S. Secret Service’s 24-hour hotline at 305-863-5050.