California Code, Public Utilities Code - PUC § 581

Every public utility shall furnish to the commission in such form and detail as the commission prescribes all tabulations, computations, and all other information required by it to carry into effect any of the provisions of this part, and shall make specific answers to all questions submitted by the commission.

Every public utility receiving from the commission any blanks with directions to fill them shall answer fully and correctly each question propounded therein, and if it is unable to answer any question, it shall give a good and sufficient reason for such failure.