Cal. Rev. & Tax. Code § 38704

The board or any person authorized in writing by it may examine the books, papers, records, and timber of any timber owner or timber operator as defined in Section 4526.5 of the Public Resources Code and may investigate the character of the business of the person in order to verify the accuracy of any return made, or, if no return is made by the person, to ascertain and determine the amount required to be paid.