How to fill Casual vacancies in the Council of States? Section 147 of Representation of the People Act, 1951
(1) When before the expiration of the term of office of a member elected to the Council of States, his seat becomes vacant or is declared vacant or his election to the Council of States is declared void, the Election Commission shall by a notification in the Gazette of India call upon the elected members of the Legislative Assembly or the members of the electoral college concerned, as the case may be, to elect a person for the purpose of filling the vacancy so caused before such date as may be specified in the notification and the provisions of this Act and of the rules and orders made thereunder shall apply, as far as may be, in relation to the election of a member to fill such vacancy.
(2) As soon as may be after the date of commencement of the Constitution (Seventh Amendment) Act, 1956, bye-elections shall be held to fill the vacancies existing on that date in the seats allotted to the States of Assam, Orissa and Uttar Pradesh and the Union territories of Delhi, Himachal Pradesh and Manipur.
Section 148. Casual vacancies in the electoral colleges for certain Union territories. Repealed by the Territorial Councils Act, 1956 (103 of 1956), s. 66.
The Representation of the People Act 1951
PART VIII
DISQUALIFICATIONS
Section 139 - 145 Chapters I to III. Rep. by the Representation of the People (Amendment) Act, 1966 (47 of 1966), s. 62
Section 146 Powers of Election Commission
Section 146A Statements made by persons to the Election Commission
Section 146B Procedure to be followed by the Election Commission
Section 146C Protection of action taken in good faith
Section 147 Casual vacancies in the Council of States
Section 148 Repealed
Section 149 Casual vacancies in the House of the People
Section 150 Casual vacancies in the State Legislative Assemblies