Counterfeit �20 and �50 Bank of England notes and some Scottish bank notes have been found in the Derbyshire area. And Nottinghamshire Police reckon some fake cash may be on its way to the South Notts area in the future.
Derbyshire Business Against Crime is passing on the warning about the notes. It advises people to check the clarity of the printing and watermark.
People are advised to feel the paper and look for a silver thread running through the note.
A Notts Police spokesperson said: "Genuine bank notes can be tested for authenticity by rubbing the large pound sign across a sheet of white paper.
"If genuine, traces of the ink will be transferred to the white paper, as the ink used never fully dries."
Police are warning people it is a criminal offence to knowingly bank, tender or keep counterfeit currency.