Police are warning retailers in Wellington to be careful when accepting larger notes from customers paying for small purchases.
It follows court appearances in the city on Monday for three Auckland men found with forged $100 and $50 notes.
One of the accused is said to have had control of 41 forged $100 bank notes.
Detective Sergeant Martin Todd says the fake notes could easily be mistaken for the real thing and retailers need to be vigilant in checking for watermarks and correct colouring.
Mr Todd says the notes have recently been found elsewhere and he will contact police in those areas to find out if there is a connection.
The Auckland men are due to reappear in court in May.