Born in Fakenham, Tann started his career with Cambridge United, after being awarded a professional contract at the beginning of the 1999–2000 season.
He made his debut in the Football League Trophy defeat to Barnet, and remained in the reserve team until the first half of the 2001–02 season, when he appeared for the Cambridge side which finished bottom of the Division Three, and winless at home.
He then signed for Gravesend & Northfleet, making one emergency appearance before moving back to the Football League with Notts County, where he scored on his debut against Bristol City in the FA Cup.
Tann was diagnosed with testicular cancer in the autumn of 2006, but following a successful operation, he returned in the latter stages of the 2006–07 season.
[3] He scored an important goal in the club's history in a 2–0 away win against Bradford City to almost keep Orient safe of a place in League One for the 2007–08 season.