Almost a third of items purchased during last week's Black Friday and Cyber Monday sales have been returned, data suggests.
And the trend could be set to continue, with a simliar amount of online Christmas purchases working their way back to seller as customers think twice about their purchases.
According to CollectPlus, 31% of purchases will be returns to their supplier this year, with the average Brit spending 52 minutes returning their online purchases.
Peak returns day is likely to turn out to have been Wednesday this week, as shoppers change their minds about their Black Friday and Cyber Monday purchases and apply for a quick refund so they can find alternative gifts in time for Christmas.
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"This will be the first peak in the immediate aftermath of these two huge online sales days and we predict this will be followed by another in the week before Christmas," says CollectPlus CEO Neil Ashworth.
"Our research tells us that the average shopper is taking valuable time and losing money each year due to complicated or costly returns. As such, it is imperative that retailers have a robust model in place to ensure that customers can conveniently return any unwanted items and are quickly reimbursed."
One in eight say they waste an average £240 every year on items they've bought online and regretted but never returned - either because they don't want to pay return postage, or because they just can't be bothered.
And the delivery itself is often problematic too. In separate research from retail software company JDA this week, it's been revealed that the UK is the worst company in Europe for missed deliveries, with more than a quarter of people saying products had failed to turn up, despite their waiting in at home.
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And, says Lee Gill, vice president of retail strategy, EMEA, at JDA, "retailers risk damaging their brand if they are unable to meet their customers' expectations when it comes to home deliveries."
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Under the Consumer Contracts Regulations 2013, which came into force this summer, goods ordered online must be delivered within 30 calendar days, unless terms and conditions specify otherwise.
Online shoppers have 14 days to return an item, up from just seven before. They can return something for any reason, even if they've just changed their minds; and if items are faulty, they should be able to get them repaired or replaced or get their money back.
Read more on AOL Money:
Online shopping: do you know your rights?
Cyber Monday: 5 ways to protect yourself from fraud
Black Friday chaos: arrests and injuries in shopping frenzy