Republic Act No. 6645

In case a vacancy arises in the Senate at least eighteen (18) months or in the House of Representatives at least (1) year before the next regular election for Members of Congress, the Commission on Elections, upon receipt of a resolution of the Senate or the House of Representatives, as the case may be, certifying to the existence of such vacancy and calling for a special election, shall hold a special election to fill such vacancy.f Congress is in recess, an official communication on the existence of the vacancy and call for a special election by the President of the Senate or by the Speaker of the House of Representatives, as the case may be, shall be sufficient for such purpose. The Senator or Member of the House of Representatives thus elected shall serve only for the unexpired term.

The Commission on Elections shall fix the date of the special election, which shall not be earlier than forty-five (45) days not later than ninety (90) days from the date of such resolution or communication, stating among other things the office or offices to be voted for: provided, however, that if within the said period a general election is scheduled to be held, the special election shall be held simultaneously with such general election.

The Commission on Elections shall send copies of the resolution, in number sufficient for due distribution and publication, to the Provincial of City Treasurer of each province or city concerned, who in turn shall publish it in their respective localities by posting at least three copies thereof in as many conspicuous places in each of their election precincts, and a copy in each of the polling places and public markets, and in the municipal buildings.

This Act shall take effect upon its publication in the Official Gazette or in at least two newspapers of general circulation.