Fake £20 notes are being used in shops in the Derry area.
That's according to the PSNI who are warning local businesses to be on the lookout for counterfeit money.
Police officers are warning the public and retail workers to be extra careful when handling cash.
They are asking people to thoroughly check all bank notes, be vigilant if anyone uses a high-value note for a low-cost item and to use UV light or a note detector pen if working on a till.
A spokesperson for the PSNI said: "Police are continuing to receive reports of counterfeit currency being passed in the Derry City & Strabane area.
"We would encourage businesses and members of the public to check any notes to ensure they are legal tender. This can be done by use of UV lights or pens and by following some of the instructions attached.
"Genuine customers will not mind waiting while you check a note is legal tender.
"If you have received counterfeit currency or if anyone tries to pass any counterfeit notes please contact police on 101 to report the incident."
Meanwhile, SDLP councillor Brian Tierney said fake money in the local community was "the last thing" any business in Derry needed at the minute.
He added: “I’d urge all businesses and members of the public to be vigilant after reports of counterfeit currency being passed in the Derry and Strabane area. I’d ask shop workers to check suspicious notes carefully and for members of the public to bear with staff and not take offence if your money is checked.
“With everything people and businesses in our communities are dealing with at the minute the last thing they need is to be given counterfeit money.
"For people who are struggling to get by every penny counts and losing money to counterfeiting could be the difference between paying for the shopping or being able to afford heat and electricity.
“Counterfeit money can also put a serious dent in businesses’ takings, particularly at a time when many are still coping with the pressures of the coronavirus pandemic.
"I’d urge businesses to equip themselves with UV Lights and pens to identify counterfeit notes and to report any suspicious activity or concerns to the police.”
