Okla. Stat. tit. 62 § 310.4
All unencumbered balances, if any, as shown by the officer charged with keeping the appropriation and expenditure records of the county, city, or town on hand at the close of day June 30, may remain as a credit for said fiscal year up to the close of day September 30, next. Said officer charged with keeping the appropriation and expenditure records of the county, city, or town shall at any time during the month of July advertise in a newspaper of general circulation in the county and shall cause to be published for two (2) consecutive times if in a daily newspaper and once if in a weekly newspaper, notice in the following form:
PUBLIC NOTICE
All persons having an indebtedness or claim against ___________________________________ _______________________________________________________________________________
County, City, or Town are hereby notified that all invoices and documentation pertaining to said purchase order or contract must be recorded in the office of _____________ Clerk on or before September 30, 20___, covering all debts now unpaid and incurred during the period beginning on July 1, 20___, and ending on June 30, 20___, or said account shall be void and forever barred.
_____________________________________
Clerk or Encumbering Officer
Provided this act shall not be so construed to allow the incurring of a new indebtedness after June 30 chargeable to the appropriation account of the immediately preceding fiscal year.
Okla. Stat. tit. 62, § 310.4