Businesses in Carrickfergus have reported receiving counterfeit £50 notes over the past few weeks.
Police say this week, that counterfeit £20 notes have been in circulation. Most counterfeit currency reports have involved Scottish bank notes, with serial number starting C.
If you have any concerns about counterfeit bank notes please call 101.
“We all want more cash. But if you or your business handle bank notes you need to take precautions that the money you are taking is genuine,” said a police spokesperson.