Omnibus Election Code
Section 22 Special election for Members of the Batasang Pambansa. - In case a vacancy arises in the Batasang Pambansa eighteen months or more before a regular election, the Commission shall call a special election to be held within sixty days after the vacancy occurs to elect the Member to serve the unexpired term.
The Batasang Pambansa through a duly approved resolution or an official communication of the Speaker when it is not in session shall certify to the Commission the existence of said vacancy.