Shops up and down the country are expected to be swamped by millions of bargain-hunters after an early push by online retailers.
Up to 7.1m shoppers are expected to hit the Boxing Day sales with one in 10 venturing out for a deal before 9am, according to research from Green Flag.
According to MoneySupermarket.com, shoppers in the UK are set to spend a total of £2.9bn.
A poll for the website found almost four million Britons (8%) plan to head to the high street on Boxing Day in addition to more than five million (10%) who will be searching online.
However, figures from one survey, by comparison website Pricerunner, suggested that almost half (47%) of those questioned were not planning on buying anything in the post-Christmas sales.
Consumers in London could struggle to get to the shops as Tube drivers prepare to strike over a dispute about bank holiday pay.
Extra buses will be laid on for those travelling to the West End, as well as the Westfield shopping centres in Stratford, east London, and White City, west London, Transport for London said.
Online retailers tried to stay one step ahead of the competition by offering heavy discounts on Christmas Day with Amazon's UK website seeing a 263% rise in sales over the last five years.
Analysts Experian predict that Christmas 2012 will be the "biggest and busiest ever" for online retailers in the UK, with visits to retail websites expected to reach 126m today, up 31% on 2011 and consumers predicted to spend £472.5m online.
But there was more gloom for the high-street in the run-up to Christmas with shoppers preferring to buy presents online, according to Business recovery group Begbies Traynor.
The British Retail Consortium (BRC) said high-street spending was "acceptable but not exceptional" this festive period – blaming it poor accessibility to high streets and weak consumer demand rather than online shopping.
Richard Dodd of BRC said: "There are a lot of myths around online retail. Ten per cent of overall retailing over the year comes from online shopping and actually it presents lots of opportunities for the retail sector."
A Begbies Traynor report said almost high-street 140 firms were in a critical condition in the fourth quarter, meaning they are on the brink of collapse, while more than 13,700 were in "significant" distress - up 35% during the three months to December 17.
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