This act contains the following provisions which are designed to ensure the integrity of the purchasing system:

• Written requisitions are required before any purchase can be made. Requisitions must be signed by the head of the department, office, or agency requiring the articles or services. Original requisitions must be kept in the office of the purchasing agent. T.C.A. § 5-14-108(k)).
• Except for emergencies, purchases and contracts are not awarded unless first certified by the director of accounts and budgets or other county official or employee in charge of the central accounting records. This certification insures that the encumbered balance in the appropriation is sufficient to cover the expense. T.C.A. § 5-14-109.
• Each purchase order or contract issued or executed must be evidenced by a written order signed by the purchasing agent. T.C.A. § 5-14-111.
• The county is liable for the payment of all purchases made in accordance with the provisions of this act, but shall not be liable for the payment of purchases made contrary to its provisions. T.C.A. § 5-14-113.