California Code, Public Resources Code - PRC § 3413

Between the first of March and the 15th of June in each year, the department shall assess and levy the charges as provided in this article.  The assessment shall be made against the person operating the property subject to assessment on the first Monday in March, except that, where the actual operation of any well has changed hands during the period for which the charge is imposed, the charge shall be apportioned to each operator upon the basis of the oil or gas produced during the period, and the lien provided for in Section 3423 shall be a lien against the property of each operator.  If the name of the owner is unknown to the department the assessment shall be made against unknown owners.

Clerical errors occurring or appearing in the name of any person whose property is properly assessed and charged, or in the making or extension of any assessment or charge upon the records, which do not affect the substantial rights of the payer, shall not invalidate the assessment or charge.