Cal. Health & Safety Code § 12108

The form of the permits shall be prescribed by the State Fire Marshal. Permits shall be numbered by the local agency issuing the permit. The permit shall include on its face the date of expiration of the permit. It shall also include a statement to the effect that any unused portion of explosives authorized by the permit shall either be returned to the source from which the explosives were obtained, destroyed, or returned to an appropriate issuing authority in accordance with Section 12087 or, in lieu thereof, application for a new permit shall be made.