He made his first-class debut in 1991 and was appointed to South Africa's national panel of referees in 1993.

He was one of the twelve referees appointed to officiate at the 2007 Rugby World Cup in France,[7] and took charge of four pool games and the semi-final between England and France, and also at the 2011 Rugby World Cup where he refereed Tonga v Canada, Canada v Japan, England v Georgia & Ireland v Italy, he was also an Assistant Referee in the Semi-final between Wales & France.

In December 2008 he was chosen as one of nine referees on a merit panel who, it was intended, would between them have charge of 75% of 2009 Super 14 matches irrespective of the nationality of the teams involved.

[9] In line with this policy, Kaplan was appointed to referee the 2009 Super 14 Final; in previous years he would have been debarred from officiating because of the involvement of a South African team.

[8] Kaplan also holds South African refereeing records for most Rugby World Cup appearances (4: 1999 (as a touch judge), 2003, 2007, 2011) and most World Cup games (13 – 5 as a touch judge) most Super 14 games (107, including 3 finals and 4 semi-finals); and most Currie Cup matches (161, including 6 finals and 4 semi-finals); and is the only referee to have won the award as South African Referee of the Year for four years in succession (2003–07)and 5 overall.