Safety
It is an offence for a supplier to sell you goods - whether new or secondhand - unless they are safe. But this does not apply to antiques or to goods needing repair or reconditioning, provided you were clearly informed of this fact. If you believe you have bought unsafe goods, you should contact the Trading Standards department of your local authority. If new goods turn out to be unsafe you may have a legal claim against the manufacturer.
If Things Go Wrong
If you decide to complain bear in mind how the item was described. A new item must look new and unspoiled as well as work properly, but if the goods are second-hand or seconds then you cannot expect perfect quality. Many shops have goodwill policies that go beyond your statutory rights. For example, some stores allow you to exchange goods that aren't faulty, such as clothes that are the wrong size. If there is something wrong, tell the seller as soon as possible. If you can't return to the shop within a few days, it's a good idea to phone the trader with your complaint.
Rejecting Faulty Goods
You have a right to 'reject' faulty goods. If you tell the seller promptly that the goods are faulty and you don't want them, you should be able to get your money back. As long as you have not legally 'accepted' the goods you can still 'reject' them - that is, refuse to accept them.
One of the ways you accept goods is by keeping them without clearly saying that you want to return them after you've had a reasonable time to examine them. What is 'reasonable' however is not fixed: it depends on all the circumstances. Normally you can at least take your purchase home and try it out. But if you delay in examining what you've bought or in telling the seller that you wish to reject the goods, then you might lose your right to reject.
Even if you signed an acceptance note, this does not mean you have signed away your right to reject the goods. If you agree to let the seller try to put faulty goods right, this also does not affect your rights. Make it clear that if the repair fails, you will be rejecting the goods and seeking a refund. You can insist on a full refund. You do not have to accept a replacement, free repair, or credit note. But if you do accept a credit note you probably won't be able to exchange it for cash later on. Some credit notes are only valid for a limited period.
Once you have, in the legal sense, 'accepted' goods you lose your right to a full refund. You can only claim reasonable compensation. Normally you have to accept an offer to put the goods right or the cost of a repair. But if the faults can't be put right you are entitled to appropriate compensation which, in many cases, may be the cost of buying an alternative.
Receipts
If you lose your receipt your rights still apply. A receipt, however, is important evidence of when and where you bought the goods and, if you don't have a receipt, some alternative proof of purchase is likely to be necessary - a credit card bill or bank statement might do. If you received faulty goods as a present, ask the person who bought them for the receipt or proof or purchase, or to complain for you.
Sending Goods Back
You're not legally obliged to return faulty goods to the seller at your own expense, unless you agreed this in advance. If a bulky item is difficult or expensive to return, ask the seller to collect it. This does not apply when you complain about faults after having 'accepted' the goods - or if the goods were a present.