Clubs will lose interchange if pre-named squads are changed from 2020
Rugby league sides who make changes to pre-named matchday squads will now be penalised by loss of an interchange, under new rules to come in next year.
While teams were previously required to name a 19-player squad by 12:00 GMT two days before a game, they can now name a pool of 21 players instead.
But if a side adds a player to the 21, they will lose one of their eight interchanges allowed in a match.
Dual registration players that have been recalled are an exception.
Any further changes would need to be approved by the Rugby Football League board in "exceptional circumstances".
The new rule applies to the Super League, Championship, League 1, the Challenge Cup and the 1895 Cup competitions.
Warrington were fined £2,000 for such a breach last season, having brought in Stefan Ratchford for the Challenge Cup semi-final against Hull FC.
Another change in the 2020 Operational Rules relates to amateur players, as professional clubs can now register up to 10 at League One level, five at Championship level and two for Super League reserve level.
Two university players are also allowed for the top tier reserve league.