Constitution of India, 1949
343.Official language of the Union.-
(1) The official language of the Union shall be
Hindi in Devanagari script. The form of numerals to be used for the official
purposes of the Union shall be the international form of Indian
numerals.
(2) Notwithstanding anything in clause (1),
for a period of fifteen years from the commencement of this Constitution, the
English language shall continue to be used for all the official purposes of the
Union for which it was being used immediately before such commencement:
Provided that the president may, during the said
period, by order authorize the use of the Hindi language in addition to the
English language and of the Devanagari form of numerals in addition to the
international form of Indian numerals for any of the official purposes of the
Union.
(3) Notwithstanding anything in this article,
Parliament may by law provide for the use, after the said period of fifteen
years, of-
(a) the English
language, or
(b) the Devanagari
form of numerals, for such purposes as may be specified in the law.