The Boxing Day sales have drawn huge crowds as High Street stores cut prices in their post-Christmas reductions.
Some shoppers queued before the doors opened
After a slow Christmas for retailers, queues formed outside many outlets throughout the UK, including shops in London, Edinburgh, and Birmingham.
Retailers reported one of the most successful starts ever to the sales, with some saying queues had doubled compared with last year.
Many were also hoping for a busier day on Thursday as more shops begin sales.
The shop sales follow online sales beginning on Christmas Day. On Boxing Day some stores, including Birmingham's Selfridges, offered discounts of up to 75% on some goods.
Some 500,000 shoppers ventured into London's West End on Boxing Day, and Selfridges' Oxford Street branch saw 9,000 customers through the doors in the first hour of trading alone.
At the Lakeside shopping centre in Essex, hundreds of cars were waiting for the centre to open at 0700 GMT.
The centre's House of Fraser reported taking more than £1,000 every minute and more than a third more shoppers compared with last Boxing Day.
Richard Dodd, from the British Retail Consortium, said: "Today is much busier than Boxing Day last year as more stores have started their post-Christmas sales early, rather than waiting till tomorrow.
"It's clear that retailers are going to have to offer bumper sales to tempt customers in, because finances are under strain this year.
"A lot of customers are reluctant to spend and there are worries about how their finances are going to stand up."
In Birmingham, 60% of Selfridges sales were taken up by ladies accessories.
A spokesman for the White Rose Shopping Centre, in Leeds, West Yorkshire, said it had enjoyed its best Boxing Day ever.
"Some stores had massive queues. It seems to be an absolutely terrific start."
Shoppers enjoyed discounts of as much as 75% on some goods
Between 30,000 and 35,000 people were expected to visit the centre on Boxing Day and Thursday was expected to be even busier. The clothing retailer Next is due to start its sale at 0500 GMT.
At Meadowhall, in Sheffield, South Yorkshire, people waited in line for at least an hour before stores opened.
MetroCentre, in Gateshead, near Newcastle-upon-Tyne, proclaimed its Boxing Day sale as the biggest one in Europe.
A spokeswoman said: "It's very positive so far. Last year we had 60,000 people and I think we'll beat that."
However, millions of shoppers have already turned their backs on the High Street to pick up bargains online.
An estimated 3.6 million people spent part of their Christmas Day searching for good deals via the internet, according to the Interactive Media in Retail Group (MRG).