Central Secretariat Service (केंद्रीय सचिवालय सेवा; abbreviated as CSS) is the administrative civil service under Group A and Group B of the Central Civil Services of the executive branch of the Government of India. They are governed by Central Secretariat Service Rules of 1962, which has been issued under the powers of Article 309 of the Constitution of India. The service members work under restrictions and rules of Central Civil Services (Conduct) Rules.
The service serves as the backbone of administrative work and provides permanent bureaucracy and functionary staff in the Union Government ministries, Cabinet Secretariat, Central Secretariat and other offices of Government of India.
Based on CSS service model, State governments like Bihar, Uttar Pradesh have organised their own independent services like Bihar Secretariat Service and Provincial Secretariat Service of UP. The Union Government ministries such like Railways, Defence and External Affairs,