As an IAS officer

Apart from serving as the Union Defence Secretary, RK Mathur served in various key positions for both Union and Tripura governments, like as the Chief Secretary of Tripura, Principal Secretary (Finance), Principal Secretary (Agriculture), Principal Secretary (Rural Development), Resident Commissioner of Tripura, Commissioner of Revenue, Commissioner of Panchayats, CEO of Tripura Tribal Areas Autonomous District Council, and as the District Magistrate and Collector of West Tripura district in the Tripura Government,^[5][6] and as the Union Defence Production Secretary, Union Micro, Small and Medium Enterprises Secretary, Special Secretary in Ministry of Defence, Development Commissioner in Ministry of Textiles, and as the Chief Enforcement Officer in Ministry of Textiles in the Union Government.^[5][6]

Mathur also served as the Private Secretary, on separate occasions, to Ministers of External Affairs and Information and Broadcasting.^[5]

Defence Production Secretary

Mathur was appointed the Union Defence Production Secretary by the Appointments Committee of the Cabinet (ACC) in September 2012,^[5] he assumed the office on 1 October 2012 and demitted it on 24 May 2013.^[5]

Defence Secretary

Mathur was appointed the Union Defence Secretary by the Appointments Committee of the Cabinet (ACC) in May 2013 for a fixed tenure of two years.^[5][7][8][9] He assumed the office of Defence Secretary on 25 May 2013 and demitted it and simultaneously superannuated from the service on 24 May 2015.^[5][6]

Chief Information Commissioner

RK Mathur was appointed the Chief Information Commissioner of India (CIC), heading the Central Information Commission (CIC), by the Appointments Committee of the Cabinet (ACC) on 18 December 2015.^[2][3][4] He took oath as the Chief Information Commissioner on 5 January 2016. He retired from the post on 24 November 2018.^[10][11][12]