The deal brings to a close a deal over a year in the making, with United first tracking the former Manchester City player mid through the 2019-20 season.
Sancho is understood to have asked for and will be given the iconic No.7 shirt, made famous by the likes of club greats George Best, Bryan Robson, Eric Cantona, David Beckham and Cristiano Ronaldo.
Edinson Cavani wore the shirt last season and will, therefore, be given a new number for the 2021-22 campaign.
With Anthony Martial’s future at the club uncertain, Cavani could end up taking his no9. The other vacant numbers include 12, 15 and 20.