Counterfeit $A50 and $A100 notes are being circulated at supermarkets, fast food outlets and pubs and clubs in New South Wales.
Police said on Friday that fake notes have been passed on the Central Coast and in the Hunter Valley 17 times this month.
They were used for a variety of purchases at licensed premises, supermarkets and fast food outlets.
Police on Friday advised business owners to be vigilant when receiving $A50 and $A100 notes as payment and to check what they are handed.
AAP reports Australian banknotes are printed on plastic and have a clear window. People should look for the coat of arms and federation star when the note is held up to the light.