So you've bought something online and discovered a problem, and now you're after a refund. What do you do?
First, of course, you approach the retailer and try to sort things out direct. But if you don't get anywhere, and you've bought the item using PayPal, you should still be able to get your money back - as long as you follow the right procedures.
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First, you have to try and resolve things with the seller, and if you're getting nowhere you have to inform PayPal within 180 days - you can do that here.
But to succeed, your complaint will need to meet certain criteria. The item must either not have arrived at all, or be 'significantly not as described'.
"For example, an item was described as new but was in fact used, or you ordered a book but received a DVD, or you ordered three items but only two arrived," says Which?.
"An item would also be significantly not as described if it was damaged in transit to you."
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And not every product is eligible. The refund policy doesn't apply, for example, to cars and other vehicles, flights, custom-made items and eBay classified advertisements.
If PayPal rules in your favour, you'll be reimbursed the full amount of the purchase, plus the original postage - but you'll have to pay for the return postage yourself.
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While PayPal's policy is generous to buyers, sellers aren't always so happy. Last year, it launched a promotions deal whereby, for a limited period, buyers were told that they could return an item if they changed their mind, with their postage refunded by PayPal.
But sellers complained that this was unfair: "There's nothing to stop some fussy buyer buying one of my daughter's grown out of, but still perfect, dresses, and deciding when it arrives they don't actually fancy the colour after all," pointed out one.
There's more information on the PayPal Buyer Protection Scheme here.