Matty Godden scored his 18th goal of the season to help Charlton secure a spot in the League One play-offs with a 2-1 victory over Northampton.
Luke Berry opened the scoring for Charlton in the ninth minute with a right-footed volley, capitalizing on a partial clearance by Northampton defender TJ Eyoma from Godden's cross.
Dara Costelloe leveled the score for Northampton shortly after, converting a penalty past goalkeeper Will Mannion after Tom McIntyre was penalized for handling Tariqe Fosu's cross.
Former Charlton player Fosu missed a great opportunity in the 53rd minute, sending his shot wide after a pass from Tyler Roberts.
Godden hit the crossbar in the 67th minute from a cross by Thierry Small, but he made amends four minutes later by calmly slotting the ball past Northampton goalkeeper Lee Burge after a flick-on by Chuks Aneke.
Northampton's James Wilson almost connected with a pass from Costelloe towards the end of the game, but Charlton held on to secure fourth place in the league table.