Does Next have to sell the items at the discounted price?
In a word, no.
The rules are that you must be shown the full price of an item, including any taxes or compulsory costs, before you buy.
As the website appeared to be showing customers the correct price at the checkout, Next does not have to honour the discounted price they were initially shown.
It’s also worth noting that online retailers often guard against price glitches in their T&Cs.
So if you spot a price glitch, don’t think you’ll be guaranteed to pay the lower price at the point you enter your card details – it could be when you get a confirmation email, some retailers reserve the right to cancel right up until delivery and others even include a specific clause in their T&Cs to cover price glitches, saying they don’t have to sell if the price was low due to an error.
So it all depends on the retailer’s T&Cs and at what point the contract becomes legally binding. See our Consumer Rights guide for more information.