When they entered circulation last year, the new £5 note was praised for being difficult to copy.
But now it has emerged the Bank of England is reportedly investigating claims that the note, which features Second World War Prime Minister Sir Winston Churchill, might have been forged.
The polymer note was launched in September 2016 and said to be cleaner, safer and longer lasting than paper notes.
It has a new generation of safety features making it harder to counterfeit, but there have been reports of forged notes circulating in Somerset - with police in the area issuing a warning.
Now the Bank of England has launched an investigation despite saying it was unaware of any forgeries of the new note.
It did say that the note’s design had been crudely copied on to paper in a very small number of cases.
A spokesman for the Bank suggested it may be possible that the fake notes were fresh, uncirculated examples of the outgoing £5 paper note - not new polymer notes.
If you are worried that you may have a fake fiver, here are six things to look for:
- Check the see-through window and the portrait of the Queen.
- Check the Elizabeth Tower (Big Ben) is gold on the front of the note and silver on the back.
- Check the foil patch below the see-through window changes from ‘Five’ to ‘Pounds’ when the note is tilted.
- Check the coronation crown appears 3D (wiggle the note to see the effect).
- Check the ultra-violet feature (a ‘5’ will appear at the bottom left when UV light is shone on it).
- Check the circular green foil patch on the back of the note which contains the word BLENHEIM - after Blenheim Palace, the birthplace of Sir Winston Churchill who appears on the note.
The advice is that if any of the above things match your current note, or if it feels unusual you should call 101 and tell the police.
Do not take the note to your local bank or building society.
Old paper £5 notes will cease to be legal tender on May 5 .
Around 165 million paper £5 notes were still in circulation in January.
Keep up to date with the latest news in west London via the free getwestlondon app.
You can even set it to receive push notifications for all the breaking news in your area.