Banks in the Western Isles became suspicious of the notes prompting an inquiry by police who have so far found no fake money.
A businessman tore up and flushed a handful of £20 notes down the toilet after his bank told him they were fake - only later the police told him they were genuine.
The man, who does not wish to be named, was among a number of businessman led to believe their cash was counterfeit on the Western Isles after bank staff became suspicious of £10 and £20 notes.
A police inquiry was launched on the Isle of Lewis three weeks ago amid fears of a well-organized counterfeiting operation.
This was followed by many of the local shops which stopped accepting £10 and £20 notes and purchased ultra-violet scanners in a bid to catch the counterfeit notes.