Before any vouchers or purchase orders are issued or contracts are entered into involving the expenditure of public funds by a state agency, the authority for the proposed expenditure shall be determined by the division and the state agency. After the authority for the expenditure is determined, the appropriate fund shall be shown by the division to be encumbered to the extent of the proposed expenditure. The division may request, and the state agency shall provide, such documentation and other information as the division deems necessary to justify the state agency’s determination of authority. The division may disapprove the proposed expenditure if it determines that the justification is inadequate or is not substantiated by law. The division may perform, on a statistical or stratified basis, internal pre-audit and post-audit procedures to monitor and enforce compliance with the provisions of this section.