As per Rules of CSS, minimum age of twenty-one years while maximum age of thirty years on the cut-off date.

While Two years relaxation in upper-age limit is acceptable for the following categories,

(a) the candidates belonging to the scheduled caste and Buddhist community
(b) the candidates belonging to the recognized Tribes who are permanent residents of the areas mentioned-below and whose families have been living in these areas,
(i) Baluchistan;
(ii) Tribal Areas of D.I.Khan and Peshawar Divisions (including former Frontier States of Dir, Swat, Chitral and Amb);
(iii) former excluded (Baloch) area forming part of the Dera Ghazi Khan and Rajanpur Districts;
(iv) former Tribal Areas of Mardan and Hazara Divisions; and
(v) Upper Tanawal Area of Hazara Division;
(c) the candidates who are permanent residents of Azad Kashmir Territory,
(d) the candidates who are permanent residents of Gilgit-Baltistan
(e) the special candidates, namely, physically impaired, hearing or speech impaired and visually impaired,
(f) in-service Government servants, armed forces personnel, contract employees, who possess a minimum of two years continuous Government service as on the cut-off
(g) Employees of nationalized banks, State Bank of Pakistan, Water and Power Development Authority, regulatory authorities, autonomous bodies and other semi-autonomous bodies are not entitled to the age-relaxation under these rules: