Online retailers are hoping that a spending frenzy will continue, with internet shopping reaching a pre-Christmas peak.
Dubbed Cyber Monday, some online stores offer discounts for consumers ramping up their Christmas shopping.
The first two Mondays of December tend to be the busiest online shopping days, after browsing over the weekend.
Cyber Monday comes after the frenzy of Black Friday offers - which some stores have carried over for a few more days.
However, some analysts say that shoppers are leaving their Christmas buying later.
This is the result of greater confidence in delivery services as retailers now rely so heavily on online sales.
Nigel Wilson, managing director of consumer insight at Experian Marketing Services, said that the pre-Christmas shopping peaks were "clearly identifiable".
Experian predicts consumers will spend £649.6m on 1 December, or £451,000 a minute - a 26% increase on Cyber Monday last year.
As the month goes on, online spending tends to be replaced by spending on the High Street for last-minute gifts and Christmas preparations. The busiest shopping day in stores is, according to Experian, on Boxing Day when traditional sales begin.
Cyber Monday is seized on by retailers' marketing arms. The same is now true of Black Friday - which originated in the US. The discounts on offer prompted some frenzied scenes on Friday.
Police criticised management of some supermarkets after crowd surges and scuffles in scenes that officers in Greater Manchester described as "totally predictable".
Online retailer Amazon UK recorded orders for more than 5.5 million goods, with about 64 items sold per second - its busiest ever day.
Some online retailers reported problems with customers accessing their websites on Friday owing to demand.