Increasing numbers of fake £20 notes are being used in the town centre and need to be stamped out, according to businesses.
Traders in Surrey Street Market and business owners nearby are concerned about a spike in circulation of fake money, especially £20 notes.
Fraudsters are targeting businesses big and small, with victims of the scam unable to claim the money back.
Esther Sutton, chairwoman of Pubwatch and landlady of the Green Dragon, said everyone needs to work together to eradicate the scam.
She said: "We've been aware of these fake 20s since October. We haven't been too badly affected, but enough to be annoying. The fakes are everywhere.
"We have a UV note detector, which is brilliant for quickly checking banknotes."
Tom Pool, who runs a fruit and vegetable stall in Surrey Street Market, said: "These notes are still floating about and it is getting a really sad thing. Everyone has taken one mistakenly.
"I thought it was all over and done with but it has come back. It would be nice if we can stamp it out."
Kez Hassan, chairman of the Old Town Business Association, added that it was important businesses train their staff in spotting the fake notes.
A police spokesman said anyone affected by this particular scam should get in contact with the Croydon Town Centre team immediately.