Here's every occasion the club have broken their record over the last twenty years, based on estimated fees...
1. 1990 - Vinnie Jones
Fee: £700k. The notorious footballing hard-man brought his tough tackling to Bramall Lane in the '90s, and has since gone on to star in over seventy films of wildly varying quality. Photo: Getty Images
2. 1996 - Don Hutchison
Fee: £1m. The Scottish midfielder joined from West Ham United, and excelled during a brief spell with the Blades, before going on to join Everton. Photo: Jamie McDonald
3. 1997 - John Ebbrel
Fee: £1.2m. The midfielder spent a decade with Everton, and had a short-lived spell with United that was brought to an abrupt halt due to a career-ending ankle injury. Photo: Laurence Griffiths
4. 1997 - Brian Deane
Fee: £1.5m. The striker spent three spells at Bramall Lane during his career. The club splashed the cash to land him for the second time in 1997, and he scored a further 11 league goals for the club. Photo: Robert Cianflone