Shoppers are expected to spend less at the Boxing Day sales as households are squeezed by the high cost of living.
Credit card firm Barclaycard predicts that the average person is set to spend £229 in the post-Christmas sales, £18 less than last year.
Bargain-hunters could also face disruption from further rail strikes which is likely to cause a build-up of traffic around shopping centres.
The AA forecasts that 15.2 million cars will be on the roads during the day.
The motoring organisation said: « Traffic is likely to build around shopping centres as lots of people seek a bargain in the sales. Meanwhile, football fans will travel to see their teams. »
It said there could be « localised » congestion, but added: « Traffic should be dispersed throughout the day as people take their time after Christmas Day. »
Network Rail workers who are members of the RMT union are holding strike action until 06:00 GMT on 27 December. Rail firms warn that services could be disrupted for much of the coming week.
A survey of 2,000 would-be shoppers by Barclaycard found that 42% said the higher cost of living would temper spending in the post-Christmas sales, with many of those saying they would spend less compared to previous years.
The rate of price rises – also known as inflation – hit 10.7% in November which was lower than October but is still at its highest for 40 years.
Harshna Cayley, head of online payments at Barclaycard Payments, said: « The rising cost of living and inflationary pressures have naturally had an impact on the amount being spent in the post-Christmas sales this year.
« Having said that, retailers can take confidence knowing that shoppers still plan to make the most of the deals and discounts on offer. »
Mike Ranson, general manager at Tessuti, a clothing store in Liverpool, told the BBC that Boxing Day remained « one of the most important days of the year for us » and was upbeat about trading in the hours ahead.
He said that the store has introduced steep discounts across its goods. « We are doing up to 50% across all brands, so we’ve got discounts across I’d say 90% of the brands across the stores. We have gone pretty big on sales this year. »
Some of the High Street’s biggest names – including Next, John Lewis and M&S – have decided to stay closed this year on Boxing Day. However, people can still shop online.
Barclaycard also found that people intend to make use of re-selling websites, such as eBay, to get rid of unwanted Christmas presents and look for bargains.
It said that 28 per cent of the people it surveyed expect to sell gifts with luxury food and drink as well as personal technology goods the most likely to be flogged-off first.