The appropriation resolution or budget, including the amounts for the payment of contract liabilities or to defray the expense of any project or purpose, shall not be construed as an approval by the board of any such liabilities or of any project or purpose mentioned, but shall be regarded only as the provisions for a fund or funds for the payment thereof when such liabilities have been found to be valid and legal obligations against the board, and when properly vouchered, audited and approved by the board, or when any project or purpose is approved and authorized by the board, as the case may be.
105 ILCS 5/34-51