CA Elec Code Section 3014

The elections official shall send a second vote by mail voter ballot to any voter upon receipt of a statement under penalty of perjury that the voter has failed to receive, lost, or destroyed his or her original ballot.

The elections official shall keep a record of each vote by mail voter ballot sent to and received from a voter and shall verify, prior to counting any duplicate ballot, that the voter has not attempted to vote twice. If it is determined that a voter has attempted to vote twice, both ballots shall be void.