Manheim Online had a record-breaking start to the year with an 11% growth in volume over its previous record.
The online aution platform, which is part of Cox Automotive, sold 5,700 units in January through 46 sales.
John Biggs, head of Manheim Online, said: "Exceeding our previous sales target is a fantastic achievement and we will continue to focus on securing the best quality stock and broadening our buyer base to improve the customer experience."
Set up in 2013, the platform sold more than 46,000 units in 2017, representing a fivefold increase on its first year in operation (8,000 units).
It connects manufacturers, leasing and fleet company vendors to buyers across the UK, offering a number of digital buying routes, to a large choice of vehicles.
Fresh stock is added to its online Buy Now catalogues twice a day, with up to 300 new vehicles listed daily.