Section 3(4) in The Official Languages (Use For Official Purposes Of The Union) Rules, 1976
(4)Notwithstanding anything contained in sub-rules (1) and (2), communications from a Central Government office in Region "C", to a State or Union territory of Region "A" or Region "B" or to any office (not being a Central Government office) or person in such State may be either in Hindi or in English:Provided that communications in Hindi shall be in such proportion as the Central Government may, having regard to the number of persons having working knowledge of Hindi in such offices, the facilities for sending communications in Hindi and matters incidental thereto determine from time to time.
