In a move that has the potential to unearth any player payment irregularities, the investigation could have severe ramifications for all NRL players.
Agents of rugby union, soccer and possibly AFL players may also be investigated, reports Australia's Daily Telegraph.
It is understood the NRL has been asked to hand over details on every player manager's dealings during the past five years.
The ATO is also scrutinising the dealings between player managers and the New Zealand Warriors salary cap scandal. New Zealand last month lost four competition points and was fined A$430,000 for breaching the NRL's salary cap last year.
It is understood the ATO has also contacted the Australian Rugby Union, requesting similar information from their managers.
