Sir Alex Ferguson revealed that Carrick, who should make his United debut against Porto or Ajax at this weekend's Amsterdam Tournament, will wear the number 16 shirt, famously vacant since the departure of Roy Keane in November 2005.
The 25-year-old England international says the move has been timed perfectly to take his career to the next level. "It's an offer that has come at the right time - professionally and personally," he said. "I felt I couldn't turn it down. This is a football decision, a decision not driven by money."
Carrick also thanked Spurs boss Martin Jol for the role played in his development as a player, adding: "I've had a great time at Spurs and the club has been brilliant for me. Martin is a great manager and has done an enormous amount for my career. Without any doubt he has helped develop me into a better player. He gave me a chance when I needed it, stood by me and I will always thank him for that."
Sir Alex said Carrick was encouraged to be given Roy Keane's old shirt number. "I said to him 'I'm giving you the number 16 jersey' so he was delighted at that," said the Reds boss. "I think that showed great courage because sometimes players are a bit superstitious about things like that but he was keen and said he would gladly take number 16."