Justice Mahajan has been an Independent Non-Executive Director of B. L. Kashyap and Sons Ltd. since December 14, 2005. Justice Mahajan was the lecturer in English at D.A.V. College, Chandigarh from 1968 to 1970. Thereafter, he commenced law practice in the Supreme Court of India and certain state High Courts, subordinate courts and other tribunals in Delhi. Justice Mahajan was appointed the Central Government counsel in the Delhi High Court from 1972 till 1977 and thereafter from 1980 upto 1988. He has been the Joint Secretary of the Delhi High Court Bar Association for two terms. Justice Mahajan was elevated as a Judge of the Delhi High Court in 1998 and retired in 2005. He holds an M.A. in English from Kurukshetra University and a LLB from Punjab University.