The financial constraints of owning two grounds led the board not to apply for promotion until the beginning of the 2005–06 season. After finishing third in 2005–06, a season in which they won the Eastern Counties League Cup, and passing the necessary ground inspection Sudbury were invited to take promotion into a resurrected Isthmian League Division One North, following the re-structuring of the National League System. Potential legal action from the Northern Premier League nearly scuppered this move, but Sudbury started 2006–07 in the new division. The management team of Gary Harvey and Michael Cheetham, who took the team up, both resigned before the season could begin, citing work and family commitments, respectively. New manager Mark Morsley was appointed in May 2006, signed from Needham Market. Sudbury's first season at this level saw the club finish in fifth place, qualifying them for the promotion play-offs. After beating Enfield Town in the semi-final, Sudbury lost to Harlow Town in a penalty shoot-out. Sudbury again qualified for the play-offs in 2007–08, finishing second in the table, but were defeated in the semi-final by eventual winners Canvey Island. In the close-season manager Morsley resigned, and was replaced by his assistant Nicky Smith.