In a tradition that has crossed the Atlantic, Mega or Cyber Monday - which falls on 2 December 2013 - is the day when internet sales are set to soar as millions join the rush to buy from online retailers such as Amazon, eBay and Play.com ahead of Christmas.
The majority of consumers will receive their last pay cheque before Christmas on Friday 29 November and then will spend the weekend browsing the shops, ready to purchase online on Monday - when many online retailers cutting their prices for one day only.
Visa Europe predicts £450 million will be spent online on Mega Monday using Visa cards, with transactions topping 7.7 million - a 16% rise on last year. This will make 2 December the busiest online shopping day ever.
"With an average of £312,500 expected to be spent online every minute on 2 December, the Christmas shopping season will certainly start with a bang," said Jeremy Nicholds, director of commercial development at Visa Europe.
High-street stores with an online presence will benefit too. Nearly two-thirds of high street retailers (63%) expect website traffic to increase by 11% on 2 December, according to a survey by Barclays. John Lewis predicts iPads, cashmere and Uggs will be the most sought-after products.
Biggest shopping day of the year
Last year, Mega Monday was the biggest pre-Christmas shopping day of the year, with the UK making 112 million visits to retail websites. Consumers spent a total of 15 million hours shopping online, according to research by Experian.
Amazon.co.uk alone saw more than 3.5 million items ordered on the site on Mega Monday 2012, at a rate of 41 items per second. A lorry packed with the day's orders left one of Amazon's eight fulfilment centres every 130 seconds.
This year, Amazon predicts that post-work Christmas shoppers will trigger a sales peak at 6pm on Mega Monday - which suggests more people will be ordering presents on mobile devices while on the go.
IMRG, the UK's industry association for online retail, reveals that mobile now accounts for 27% of online spend - a rise of 2,000% since the start of 2010.
"The expected peak in sales at 6pm on Cyber Monday is interesting as traditionally sales have spiked later in the evening," said Xavier Garambois, vice president of EU Retail at Amazon. "In fact, in 2011, sales peaked at 9.20pm.
"The earlier rush indicates that people will be using their commute to get a head start on their shopping or logging on as soon as they get home, so they can relax in the knowledge that their Christmas shopping is done."
And look out for special deals on Mega Monday. For example, online retailer Play.com promises to have Mega Monday deals on every Monday between now and 19 December. Deals so far have included £70 off an Apple iPad Air, which was priced at £329. It has also offered the Sony PS Vita with Tearaway, Little Big Planet and a 16GB memory card for £139.99 - a discount of 17%.
Hotukdeals.co.uk are already listing Mega Monday deals, which include savings off iPads, laptops, DVDs and clothes. Current offers include 25% off all SodaStream Drinks Makers and 20% off Slendertone products.