Proper storage of refund books required; maintain voucher issue records and ensure documented handing over on change of incumbent. Proper storage and custodial control of refund books is mandated, requiring maintenance of a clear record of issue and utilization for refund vouchers and secure custody of refund books containing used or blank vouchers. On change of office incumbent by transfer, retirement or other reason, there must be an orderly and documented handing over of refund books; officers in the region are to be informed for strict compliance with the Manual of Office Procedure and prior Board instructions.