They receive payment from the leagues for their work. The invoicing for game fees is handled differently by every league or tournament. The pairing of officials and matches is performed by an assignor. Assignors are also contracted by leagues or tournaments to produce the assignments. Assignors are usually compensated on a per game basis by the league.
Assignors have a predetermined pool of prospective referees that they intend to work with.
This pool is usually determined by geographic proximity in and around the area in which the league's matches are played. The pool may also be determined to some extent by the qualifications of the referees. Although referee grade is a measure of qualification, it does not sufficiently discriminate among referees for the assignor's needs. Before an assignor can pair referees with matches, the schedule of matches must be defined. This function is performed by the leagues.