The NRL has reportedly refused to register Sam Burgess' big money deal with South Sydney, with the club being ruled to be over the salary cap.

The Seven Network on Thursday night reported the game's governing body had found that even with Dylan Walker's release from the final year of his playing contract, the Rabbitohs were still over the player payment limit for 2016.

After a stint with English rugby union, Burgess was lured back to rugby league on a three-year deal, described as the richest in the game's history and believed to be worth $1.5 million a season.