Section 3(2)(ii) in The Indian Police Service (Pay) Rules, 2007
(ii)Appointment of a member of the Service in the scales of Selection Grade and above shall be subject to availability of vacancies in these grades and for this purpose, it shall be mandatory upon the State Cadres or the Joint Cadre Authorities, as the case may be, to seek prior concurrence of the Central Government on the number of available vacancies in each grade.