Police are trying to identify three men who may be able to help their inquiries after fake £50 notes were handed to staff at the Holbeach Co-op.
Police say the incident happened at the Fleet Street store at 8pm on February 27 when attempts were made to pay for a selection of items using the fake notes.
CCTV images have been released and police are appealing to the public for any information that could assist the enquiry as well as the names of the men pictured.
Anyone who can help can call 101, quoting incident number 426 of 27 February, and say this is for the attention of PC 605 Wharton.
Information can also be given to Crimestoppers anonymously on 0800 555111.