Okla. Stat. tit. 62 § 485
It shall be unlawful for the governing board of any city or town to issue any warrant or certificate of indebtedness, in any form, in payment of, or representing or acknowledging any account, claim or indebtedness against such city or town, or to make any contracts for, or incur any indebtedness against such city or town, in excess of the amount then unexpended and unencumbered of the sum appropriated for the specific item of estimated needs for such purpose theretofore made, submitted, and approved, or authorized for such purpose by a bond issue. All warrants upon the lawful treasurer, for a city or town purpose, shall be issued upon the order of the governing board thereof, drawn by its clerk, signed by the chairman or lawfully designated presiding officer thereof, and the clerk. Each warrant shall be coded in such manner as may be necessary to designate the fund and appropriation upon which it is drawn. The signatures of the presiding officer and clerk shall be deemed as notification to the public that the warrant is for the purpose and within the amount of the appropriation charged.
Okla. Stat. tit. 62, § 485