The Trade Descriptions Act only actually does what it says on the ‘tin’ … provides legislation about descriptions, and remedies for misdescriptions.
The legislation covering your rights as a consumer when buying goods was, historically, provided (in the UK) by the Sale of Goods Act, which dates back to the 19th Century, and was most recently overhauled in a major way by the 1979 version of the SoGA. But it has then been added to by several other bits of law, most notably by the Consumer Protection (Distance Selling) Regulations 2000, more commonly referred to as the Distance Selling Regs, or DSR. This was the UK implementation of, in those days, an EU directive.
Most of this has effectively been ’codified’into the newer Consumer Rights Act 2015.
Nor is the 12-month period strictly accurate. It’s more complicated than that because it depends on where/how you bought, and if you’re returning something, why you’re returning it and how quickly.
Most manufacturers offer a 12-month guarantee, but they’re not obliged to, and some offer considerably more than that. But as a consumer, your first port of call for problems is always the business you bought from (usually a retailer but could even be the manufacturer). because that’s who you have a contract with. Unless you bought direct from manufacturer, you don’t directly have a contract with them. However, IF they offer a warranty, and you knew of it when you bought and relied on it at that time, then it can be enforced.
But mostly, the contract is with the retailer. If you bought online, or ia some other “distance” method (maybe, mail-order catalogue) then you have 14 days, starting when you receive the goods, to simply change your mind, and send them back. There are some exclusions, and some restrictions, but generally, you get a full refund (but you usually pay for return shipping). That applies even when the goods are not faulty, and you aren’t even required to give a reason.
Then, there is a 30-day period (in the legislation, not because Amazon say so) during which you can return goods that “do not conform to contract” (e.g. are faulty in some way) for a full refund. This is known as rescission. After that 30-day period, the initial situation is that the supplier can offer repair, replacement or even a partial refund, though you can’t insist on a given option especially if it is unreasonably difficult or expensive. Furher options exist if any such replacement, for instance, is also defective, so a retailer cannot keep replacing an item again, and again.
But at that stage, we’re talking about “faulty” goods, or more technically, goods that do not conform to contract. The next issue is WHY they don’t conform to contract. For the first 6 months, faulty goods will be presumed (by the legislation) to have been faulty when supplied (i.e. the fault is “inherent”) unless the retailer can prove otherwise. That’s when the repair/replacement bit kicks in.
But after 6 months, the legal presumption is that the goods were NOT faulty when supplied … unless the buyer can prove they were. That may end up requiring an inspection/report by a third-party expert. You, the buyer, have to pay for that, though if it supports your assertion that the goods were “inherently” faulty (i.e. when you bought them) you can usually get the seller to refund you the cost of the report as well.
Finally, all the above applies for up to 7 years from purchase (in England and Wales, Scotland IIRC is slightly different as to when the clock starts ticking, and is for 6 years).
Bear in mind, everything I said above is based on some pretty broad generalisations and there are variety of complexities in detail. For instance, I’m referring to goods, and services are different. Also, the 7 years refers to the periofd under which you can sue for breach of contract, but exactly how long goods should last depends on the nature of the goods, and terms like “reasonable period” are littered in the legislation. But it makes sense when you think about it - a car and a banana are both “goods” but it’s not reasonable to expect a banana to last several years. You would also probably be justified in expecting a £30 t-shirt from a quality brand to last longer than a £1.50 t-shirt from a street market. And so on.
But in short, the 12-month thing is illusory, in relation to retailers. Manufacturers can offer that, and be held to it in the situation I mentioned above. Retailers can offer 12-months if they wish, but aren’t onbliged to. If they do, you can hold them to it. These sorts of optional guaranties are distinct from your legal rights. But retailers are bound to the rights I outlined (very roughly) above, whether they like it or not, provided you bought as a consumer (not another business) because they are your consumer rights, embedded in legislation, and they are (depending on the nature of the goods, and the fault) for potentially much more than 12 months.
Oh, and for the avoidance of doubt - I AM NOT A LAWYER. This post is comment/opinion, by some bloke on the internet, and should not be construed as legal advice. If anyone wants legal advice, my only advice is to consult an actual lawyer.