Retailers could bag £10.5bn in five years if they made online buying easier for their customers.
Research by Barclays has found that online shoppers leave £3.4bn in virtual shopping baskets every year in the UK, and never make it to the check-out.
Retailers could seize this money if they made their websites easier to navigate, Barclays said.
Creating a more streamlined service for consumers would make nearly a third (28 per cent) of online shoppers more likely to complete their purchase.
One of the key problems is that people fail to follow through on purchases if they switch from a mobile onto a laptop to pay. Barclays is urging retailers to boost sales by making mobile sites easier to use.
However, it seems there isn't a huge appetite from retailers to invest more money into mobile shoppers.
Mobile is one of the fastest-growing areas in retail, but only 16 per cent of retailers plan to make mobile sales a top priority in the year ahead.
Ian Gilmartin, head of retail at Barclays said: “At a time when cost management is a priority, it’s understandable that investment in mobile optimisation may seem too expensive for many retailers. However, our research underlines the longer term benefit of providing easy to use options across all online platforms.
"By adapting quickly to the needs of today’s consumer to create a better shopping experience online, and particularly via mobile, retailers will boost their sales.”