 Millwall bought Carter in 1987 for £15,000 from Queens Park Rangers and gave him his Football League debut in a 0–0 draw with Oldham at The Den in the Second Division.He quickly established himself in the Millwall first team and was an integral part of the team which gained Millwall promotion to the top flight in 1987–88, the first time ever in Millwall's 100-year history.Carter was part of a side that included players such as Teddy Sheringham, Tony Cascarino and Terry Hurlock.