Change made to number of sets played and use of tie-breakers. Men’s National Championship finals now just three sets.

The APTA moved to a best-of-three sets format for the men’s national ranking and National Championship events. Many ranking events had already adopted this format. The 12 point Tiebreak was recommended for all sets except for the third set in the finals of the Men’s, Women’s and Mixed National Championships which were to be played out.

See also 1984 rule change for Men’s National Championship

Source: Platform Tennis News, Summer 1989