Section 25A(b) in Uttar Pradesh Municipal Corporation Act, 1959
(b)if a person after his election as Mayor, [Deputy Mayor] [The word 'Deputy Mayor' omitted by U.P. Act 49 of 2007, S.8.] or Corporator subsequently elected or nominated to any of the offices referred to in clause (a) he shall on the date of first publication in the Gazette of India or of the Uttar Pradesh of the declaration of his election or his nomination, cease and within a period of fourteen days from such notification intimate by notice in writing signed by him and delivered to any person authorised by the Government in this behalf, submit his option, in which office he wishes to serve and any choice so intimated shall be conclusive, failing which he shall upon expiry of said period, to hold, the office of Mayor, [Deputy Mayor] [The word 'Deputy Mayor' omitted by U.P. Act 49 of 2007, S.8.] or Corporator and a casual vacancy shall thereupon occur in the office of the Mayor, [Deputy Mayor] [The word 'Deputy Mayor' omitted by U.P. Act 49 of 2007, S.8.] or Corporator as the case may be.]