Approval and requisition of services under section 132 require Form No. 6C, reasons, and a designated approval number. Approval and requisition procedure is prescribed for the use of services, and for references to persons, entities, or registered valuers, under section 132. The authorised officer may requisition such services or make such reference for the statutory purposes covered by the provision, after approval by the specified senior tax authorities. Applications are to be made in Form No. 6C, disposed of within six months, and approved persons are issued a Designated Approval Number.