The unhappy customer shared their experience on Reddit’s AusLegal page, explaining that they entered a Coles supermarket in Victoria with a trolley containing groceries from Aldi.

“I had a trolley full of items I had bought at Aldi, and popped into Coles for a few bits,” the poster said.

“The lady at the self-checkout pointed at the 30-pack of Coke cans and demanded to see a receipt to prove I didn’t steal it.

“I said I didn’t have one, I never keep receipts unless it’s for an expensive purchase that I may need to refund/exchange.

“She continued insisting that I had to keep my receipts from other stores so that I could prove I hadn’t stolen.”

9News.com.au asked criminal defence attorney and author of Talk Your Way Out of Trouble, Jahan Kalantar, the question.

Turns out supermarkets have little to no power to demand a receipt from a customer.

Kalantar mentioned that legal regulations do not empower private retailers such as Coles and Woolworths to demand a receipt for items bought at different stores.

”If the store thinks that you’ve stolen, they can request to inspect your bags, but security guards really don’t have much power; all they can do is get the police involved.

“If they keep people there against their will, if the Coles worker keeps you there, there’s a possibility that it might be a false imprisonment claim.”

Kalantar said most people would just comply and show their receipt to get out of the situation.

There is a bit of a grey area if you paid cash or don’t have a receipt, if they suspect you’ve stolen an item.

“I had one where the guy didn’t have his receipt, but he just opened his bank account and said here is the transaction, I couldn’t have taken it,” Kalantar said.

“But fundamentally, you are entitled to your privacy, just because you walk into a store and they have some assumption doesn’t mean anything.

“It’s very different if they’ve seen you on camera pocketing something, but there is no fundamental legal authority that a security guard can compel you to provide a receipt from a different store.”

9News.com.au has contacted Coles for comment.