Avon and Somerset Police are warning city centre coffee shops and small independent businesses in Bath to be on the alert for fake £50 notes.
There have two incidents this week, at Intermezzo Express in Barton Street and Made by Ben in Walcot Street, where three men have ordered food and drink and paid separately with £50 notes that turn out to be counterfeit.
The men spoke with Irish accents and all wore gloves.
Shop staff are advised to be vigilant and to check all large demonination notes for their serial numbers and paper quality.
Anyone with information or who sees anyone suspicious is asked to call Bath city centre neighbourhood police on 101 or 999.