2018–19 Spartan South Midlands Football League Premier Division

At the end of the 2017–18 season, the following teams left the division:
 * Promoted to Step 4
 * Berkhamsted, to Southern League East
 * Welwyn Garden City, Southern League East
 * Transferred within Step 5
 * Hoddesdon Town, to the Essex Senior League
 * Holmer Green, to the Hellenic League
 * St Margaretsbury, to the Essex Senior League

The remaining 16 teams, together with the following, form the Premier Division for season 2018–19:
 * Promoted from Step 6
 * Baldock Town, from Division One
 * Potton United, from United Counties League Division One
 * Transferred within Step 5
 * North Greenford United, from the Combined Counties League
 * Relegated from Step 4
 * Arlesey Town, from Southern League East