There are reports of fake £20 notes circulating in the Furness area.
Police said incidents had been reported in Barrow, Ulverston and Askham.
It is suspected two young people, both male, may be targeting businesses by using fake £20 notes to pay – and taking real money as change.
The men spoke with an accent not local to the area, potentially Irish.
Police said they would urge people and businesses to be alert and not to accept any money that does not appear to be real.
People are asked to report any incidents to Action Fraud on 0300 123 2040.
