Police are investigating the use of a counterfeit $100 note in Whyalla on Saturday.
About 3.30pm on Saturday 7 May, the note was used to buy items at a shop.
After the person who handed over the note had left the store, the note was inspected further and found to be fake.
Enquiries continue regarding the person who handed over the note.
Police are asking local businesses to be vigilant when receiving cash and take the time to inspect any money to ensure it is legitimate.
To determine if a suspect note is counterfeit, it is best to compare it with a note that is known to be genuine.
Anyone who receives counterfeit money can contact police on 131 444 or attend their local police station to report the matter.
Handle the note as little as possible and store it in an envelope.
Check any CCTV for footage of the suspect and provide police with any other relevant information such as description of the suspect, anyone else they were with, and their vehicle.