NRL Head of Football Elite Competitions Graham Annesley goes through the rules and regulations stipulated by the NRL for the addiction of the 18th player for all clubs
The 18th player can only be used if your club name contains the words Roosters, Rabbitohs, or Storm.
For other clubs the only exclusion is if the game falls on the first Tuesday after a full moon, after the 12th of December, on a leap year, and only if the 12th of December is actually a Friday.