Self-service checkouts in supermarkets have become the quick and effective way to buy your shopping without having to wait in a long queue.
Although they sometimes pose some issues or have a technical mishap, they have become the new normal for many customers.
However, this easy method is often reliant on customers to be truthful about their purchases, Devon Live writes.
Although supermarkets put measures in place in order to stop people cheating the system, some things may go unnoticed - just like one woman has discovered.
The flaws in the system were brought to light by a shopper who wrote into News.com.au's Sisters In Law, who shared her sneaky trick in order to save some money.
After sharing her 'hack', the woman was warned that the law is the law, and her trick could land her in trouble.
A woman wrote into News.com.au's Sisters In Law, which allows people to put their legal conundrums to sisters and lawyers Alison and Jillian Barrett, about a disagreement she had with a friend.
She said that when her friend uses the self-service checkouts, she regularly puts more expensive fruit and veg - such as an avocado - through the system as a brown onion instead.
The friend believes that it isn't stealing as she's still paying something for it and claimed the supermarkets work the cost of self-checkout fraud into its prices because "everyone does it".
The lawyers replied to advise: "It doesn't matter how your friend tries to justify her behaviour, her deceitful conduct in intentionally not paying full price is against the law.
"Your friend's technique of using the self-service checkout to pass off more expensive items as cheaper ones cheats the system by underpaying. Her fraudulent behaviour is just one of many tricks employed by self-service thieves to avoid payment."
Alison and Jillian, based in Australia, said the 'tricks' are costing supermarkets a fortune every year and are actually pushing up the prices of groceries as a result.
Self-checkouts can weigh items to check you're being truthful, and supermarkets often employ staff and security guards to ensure they are being used correctly - but they also rely on the honesty of their customers.
They warned that "an excuse like getting avocados confused with brown onions is likely not going to cut it" if her friend is eventually caught, and she could being left facing a range of punishments.
In Australia, the legal experts advised that the act can carry either a fine, having to pay for the items and apologise to the store, or even criminal charges if she fails to comply or is a repeat offender.
They conclude: "You have to ask, is saving a few dollars on avocados worth the risk?"
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