In the last few weeks, there have been several reports of counterfeit cash being used to pay for second-hand goods and takeaways.
Whilst most reports have been from York, North Yorkshire Police believe the currency may be used elsewhere in the county too and is warning the public.
The fake banknotes have been used to pay for second-hand items bought through Facebook Marketplace and eBay as well as for food and takeaways.
North Yorkshire Police say the currency is very crudely created and the notes tend to be opaque and much thicker material than authentic notes.
Many of the notes have also been printed ‘Poonds’ instead of ‘Pounds’ and some even feature the small print: ‘This money is play money for video movie use only’.
A spokesperson said: "We’re urging the public to be extremely careful when accepting cash payments and to check that notes are genuine."
An investigation into the counterfeit notes is currently ongoing and if you think you have been paid using counterfeit currency, call 101 to report this quoting reference number: 12210103581.
The Bank of England have the following advice around checking for genuine notes:
* Tilt the note from side to side. Check the images change between a ‘£’ symbol and the number ’20’.
* Hold the note up to the light. Check there is a bright ‘£20’ at the top of the Queen’s portrait.
* There are alternating images of Adam Smith along the foil strip. The position of foil patches can vary on notes. To the right of the Chief Cashier’s signature, the number ’20’ is embossed over the foil strip.
* The note is printed on special paper that gives it a unique feel. On the front of the note, you can feel raised print. For example, on the words ‘Bank of England’ and in the bottom right corner, around the number ’20’.
* Under a good quality ultra-violet light, the number ’20’ appears in bright red and green on the front of the note, against a duller background. You can see bright red and green flecks on both the front and back of the note.
* A metallic thread is embedded in the note and appears as silver dashes on the back. When the note is held up to the light, the thread appears as a continuous dark line.