(a) The governing authority of each county, municipality, and other political subdivision of the state may enter into a contract for a lock box system with any bank in this state to have the bank receive, process, and deposit mailed tax returns and payments.

(b) In any county of this state in which the county tax collector or tax commissioner receives mailed tax payments or otherwise collects taxes for the county as well as for one or more municipalities lying wholly or partially within the county, the county tax collector or tax commissioner may enter into a contract for a lock box system described by subsection (a) of this Code section on behalf of the county and any such municipality, provided such contract is approved by the governing authority of the county and by the governing authority of any municipality whose tax payments are covered by such contract. A tax collector or tax commissioner and any such officer's surety shall not be liable for any tax payments mailed directly to a bank as the depository under a contract for a lock box system authorized by this subsection. Any contract for a lock box system under this subsection shall require a detailed accounting by the depository of all tax payments received by the depository and shall provide for such other matters as may be necessary to fully protect the interests of the taxpayers, tax officials, and local governing authorities affected by the contract for a lock box system.