law: Cost and Works Accountants Act, 1959 
  13. Resignation of membership and casual
  
  vacancies 
  (1) Any member of the Council may at any time
  
  resign his membership by writing under his hand addressed to the President, and
  
  the seat of such member shall become vacant when such resignation is notified
  
  in the Official Gazette.
  (2) A member of the Council shall be deemed to
  
  have vacated his seat if he is declared by the Council to have been absent
  
  without sufficient cause from three consecutive meetings of the Council, or if
  
  his name is, for any cause, removed from the Register under the provisions of
  
  section 20.
  (3) A casual vacancy in the Council shall be
  
  filled by fresh election from the constituency concerned or by nomination by
  
  the Central Government, as the case may be, and the person elected or nominated
  
  to fill the vacancy shall hold office until the dissolution of the Council:
  PROVIDED  that no election shall be held to fill
  
  a casual vacancy occurring within six months prior to the date of the
  
  expiration of the duration of the Council, but such a vacancy may be filled by
  
  nomination by the Central Government after consultation with the President of
  
  the Council.
  (4) No act done by the Council shall be called
  
  in question on the ground merely of the existence of any vacancy in, or defect
  
  in the constitution of, the Council.