Okla. Stat. tit. 19 § 890
The board shall then levy an annual assessment sufficient to pay the interest of the outstanding bonds, as it falls due, and also to constitute a sinking fund for the payment of the principal of the bonds in the amount set forth in the resolution providing for the issuance of the bonds, plus a reserve for delinquent assessments in the amount of ten percent (10%), and said board shall continue to levy such assessments until all bonds issued by said district and the interest thereon have been paid in full. The board shall also levy an annual assessment sufficient to care for the cost of operation, repair and maintenance of the district and its equipment, and for payment of the salaries of the officers and employees of the district, provided that no such annual assessment for operation, repair, maintenance and salaries shall exceed ten (10) mills on the dollar of the gross assessed value of all real property in the district; provided, if Article X, Section 8 of the Oklahoma Constitution requires one hundred percent (100%) of fair cash value to be taxable for purposes of ad valorem taxation, the maximum number of mills authorized by this section shall be two (2) mills. For the purpose of determining the amount of the assessments levied and collected annually for cost of operation, repair, maintenance and salaries, the board of directors shall prepare annually a budget of such expenses and shall approve and adopt such budget by a resolution duly passed and entered on its record. The clerk of the board must compute and enter in separate columns of the assessment book the respective sums of dollars and cents in each fund to be paid on the property therein enumerated and no earlier than the first day in July and no later than the tenth day in July in each year the clerk shall certify to the county treasurer the amount of taxes in each fund levied upon each tract of land by said board and said county treasurer shall enter the amount of each fund in separate columns of the tax list of his county and said taxes shall be collected by the county treasurer at the same time and in the same manner as all other taxes are collected in this state. Provided, that no such certification shall be made to the county treasurer unless the clerk of the board shall have sent a notice of the nature and amount of the assessments by restricted delivery mail on or before June 1 of said year to the last-known address of the owner of the assessed property. All such taxes collected or received by the county treasurer shall be paid by him to the clerk of such district. All taxes assessed as aforesaid shall be a lien against the special tracts of real property on which they have been assessed until paid, and said lien shall be coequal with the lien of ad valorem taxes and all other taxes, including special assessments, and prior and superior to all other liens. The statute of limitations shall not apply.
Okla. Stat. tit. 19, § 890