New consumer protection measures - including longer refund rights - have come into force under the Consumer Rights Act.
For the first time anyone who buys faulty goods will be entitled to a full refund for up to 30 days after the purchase.
Previously consumers were only entitled to refunds for a "reasonable time".
There will also be new protection for people who buy digital content, such as ebooks or online films and music.
They will be entitled to a replacement, if the downloads do not work, but not a refund.
If a download also infects a computer with a virus, the provider could also be liable to pay compensation for getting the virus removed.
The Act also covers second-hand goods, when bought through a retailer.
People buying services - like a garage repair or a haircut - will also have stronger rights.
Under the new Act, providers who do not carry out the work with reasonable care, as agreed with the consumer, will be obliged to put things right.
Or they may have to give some money back.
In many cases retailers offer to refund goods even when they are not faulty - for example if customers change their minds about a product - but there is no statutory right to a refund.
'Fit for purpose'
"The new laws coming in today should make it easier for people to understand and use their rights, regardless of what goods or services they buy," said Gillian Guy the chief executive of Citizens Advice.
When disputes occur, consumers will now be able to take their complaints to certified Alternative Dispute Resolution (ADR) providers, a cheaper route than going through the courts.
Examples of this include the Consumer Ombudsman, which is free to use for consumers. However not all retailers are signed up to such ADR providers.
The Consumer Rights Act says that goods
- must be of satisfactory quality, based on what a reasonable person would expect, taking into account the price
- must be fit for purpose. If the consumer has a particular purpose in mind, he or she should make that clear
- must meet the expectations of the consumer
The Act has been welcomed by many consumer rights groups and further information can be found here.
"Now, if you buy a product and discover a fault within 30 days you'll be entitled to a full refund," said Hannah Maundrell, the editor of money.co.uk. "The party really is over for retailers that try to argue the point."
The Act also enacts a legal change that will enable British courts to hear US-style class action lawsuits, where one or several people can sue on behalf of a much larger group.
It will make it far easier for groups of consumers or small businesses to seek compensation from firms that have fixed prices and formed cartels.