Discovery powers permit tax authorities to compel inspection, attendance and production and to impound documents with safeguards. Prescribed tax authorities are vested with court-like discovery powers under the Code of Civil Procedure for purposes of the Act-including discovery, inspection, compelling attendance and production of books and documents, and issuing commissions-and may exercise those powers during inquiries or investigations whether or not proceedings are pending. Such authorities may impound and retain produced books and documents subject to rules, and tax officers below Commissioner rank must record reasons for impoundment and obtain senior approval to retain records beyond thirty days.