The Bank of England has launched a probe into the reports of the fake notes.
It was believed the new polymer £5 note was impossible to counterfeit when it was put into circulation in September.
It is thought the design of the polymer notes may have been transferred on to paper by would-be fraudsters.
The old paper Bank of England £5 notes that feature Elizabeth Fry will cease to be legal tender on May 5.
If you’re worried you might have a counterfeit new £5 note here are a few things you can check.
Check the coronation crown appears 3D (wiggle the note to see the effect).
Check Big Ben is gold on the front of the note and silver on the back.
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.
Check the see-through window and the portrait of the Queen.
Check the foil patch below the see through window changes from ‘Five’ to ‘Pounds’ when you tilt the note.