In the 13 years that IMRG and Capgemini have tracked online sales in their e-Retail Sales Index, the research has never discovered as much sales growth between August and September as it did this year. The index found that online purchases rose by 13 percent in that period, and by 20 percent between 2012 and 2013. 

This record was set strongly in part by mobile devices. Smartphone and tablet adoption has continued steadily, and m-commerce has expanded with the trend. Notably, consumers appear to be increasingly comfortable buying products on their smartphones, as as these gadgets accounted for 23 percent of all mobile sales in September, up from 15 percent in August. 

"The fact that e-retail has seen its sharpest period of growth for September suggests that consumers are shopping with confidence," said Chris Webster, Vice President and Head of Retail Consulting and Technology at Capgemini. 

As mobile devices achieve a larger share of online sales, retail industry professionals will want to adapt to changing consumer habits and ensure that their point of sale software is set up for smartphone- and tablet-based purchases.