Hypothetically, if a self-service checkout at my local Tesco were to be malfunctioning and selling items for half-price, and if someone were to exploit this to buy cheap goods, would this be considered theft under UK law?

In the Theft Act 1968:

A person is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it.

Does the purchase of goods at half the marked price constitute dishonest appropriation? An argument that it doesn't might be that the self-service checkout has authorized the purchase and the requested amount has been paid, thus there is no dishonesty involved.

However, the checkout is obviously not intended to operate this way, and the price shown by the checkout obviously doesn't match that of the displayed price in the shop. Does this mean that by knowingly still buying goods like this, the purchaser is being dishonest?

  • Note that if the price at checkout is not the same as the displayed price in the shop, it is the one at check out that is the correct price. This is a general retail rule, the displayed prices in the shop do not give you any right to purchase at this price. Only check out counts, if you don't like the check out price you can still back out of the purchase.
    – quarague
    Oct 26, 2020 at 21:07

2 Answers 2


The word "dishonestly" is defined in the act

(1)A person’s appropriation of property belonging to another is not to be regarded as dishonest—

(a)if he appropriates the property in the belief that he has in law the right to deprive the other of it, on behalf of himself or of a third person; or

(b)if he appropriates the property in the belief that he would have the other’s consent if the other knew of the appropriation and the circumstances of it; or

(c)(except where the property came to him as trustee or personal representative) if he appropriates the property in the belief that the person to whom the property belongs cannot be discovered by taking reasonable steps.

(2)A person’s appropriation of property belonging to another may be dishonest notwithstanding that he is willing to pay for the property.

The prosecution thus must establish that defendant knows that he has no legal right, that is, it must be established that he knows that it is not a legal purchase. The simple act of purchasing in these circumstances provides no proof of the alleged dishonesty: the prosecution must add something else. For example, testimony that defendant declared "Crikey! This machine is giving me half-off on everything, those suckers! I wish I had bought more" might be sufficient to establish dishonesty. The "intent" of management in installing these machines is legally irrelevant, indeed management's intent is to reduce operating costs. It is management's responsibility to ascertain that the machines function the way they wish them to. It is not self-evident to the defendant that the machine is malfunctioning, but defendant could have actual knowledge that makes the transaction dishonest.

  • I don’t think it would make it dishonest regardless because of the machine is selling at those prices then I think that creates a binding contract which in reality does legally bestow that property onto the purchaser. Correctly believing that one has the legal right to appropriate satisfies one of the inclusive-or conditions. Furthermore it is debatable whether in such circumstances they would be thief is approaching anyone else’s property in the first place, much less doing so dishonestly. If the machine creates a legal sale then it is no longer Oct 18, 2023 at 1:52
  • another’s property and therefore the theft act’s various provisions cease to be relevant anyway. Oct 18, 2023 at 1:52

It would seem to be extremely difficult for the prosecution to prove dishonesty in this example. Tesco regularly has complex offers and discounts that shoppers don't notice or understand, resulting in discounts being applied at the checkout that they did not necessarily expect.

More over buying mis-priced items is not theft. Before self service checkouts the clerk would have had an opportunity to check the price and their acceptance would have made the sale final. In fact self service checkouts do have clerks, both on the shop floor and in a back office where they can see all transactions in real-time.

There is no responsibility on the buyer to check that prices are what the seller desired, and accepting an offered price, even if it seems very good, is not dishonest.

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