State Bank of India Act, 1955
23. Vacation of office of directors, etc
If a director of the Central Board or a member of a local Board or a Local Committee-
(a) becomes subject to any of the disqualifications mentioned in section 22; or
(b) resigns his office by giving notice in writing under his hand, in the case of 26[chairman, vice-chairman and a managing director], to the Central Government and in the case of other directors or members of Local Boards or Committees, to the Central Board, and the resignation is accepted; or
(c) is absent without leave of the Central Board, the Local Board or the Local Committee of which he is a director or member, as the case may be, for more than three consecutive meetings thereof ;
his seat shall thereupon become vacant.