When the excise board shall have ascertained the total assessed valuation of the property taxed ad valorem in the county and in each municipal subdivision thereof, and shall have computed the total of the several items of appropriation for general fund, sinking fund, and other legal purposes for the county and each municipal subdivision thereof, said board shall then proceed to compute the levy for each fund of each municipality. The procedure for the computation of such levies shall be as follows:

First: Determine the total amount of the several items of appropriation for each fund.

Second: Deduct from such total appropriation the actual cash fund balance of the immediately preceding fiscal year.

Third: Deduct from the remainder thus ascertained the estimated probable income from sources other than ad valorem taxation; however, in no event shall the amount of such estimated income exceed ninety percent (90%) of the actual collections from such sources for the previous fiscal year. Provided, that the amount of such estimated income for a school district may be the amount that is chargeable as minimum program income of the district for the purpose of receiving state equalization aid. Also, deduct the estimated probable revenue to be derived from additional collection from taxes in the process of collection of the immediately preceding taxable year; provided that the amount so estimated shall be cash fund balance as hereinafter defined, and shall include none of that portion of the reserve added at the beginning of such year for delinquent tax, and shall not exceed ninety percent (90%) of the actual collections of additional back taxes legally accrued to and credited to the same fund account of the immediately preceding fiscal year.

Fourth: Add to the remainder a reserve for delinquent taxes, the amount of which reserve shall be determined by the excise board, except for any municipality which has opted by resolution to come under the provisions of Section 17-201 et seq. of Title 11 of the Oklahoma Statutes, in which case the governing body of such municipality shall determine the needs of the municipality for sinking fund purposes, after taking into consideration the amount of uncollected taxes for the previous year or years; provided that the reserve so added shall not exceed twenty percent (20%) or be less than five percent (5%); and provided, further, that the reserve so added shall not be subject to review.

Fifth: Compute the levy necessary to raise an amount of money equal to the remainder thus ascertained, based upon the total assessed valuation of the county or subdivision thereof, taking into consideration any deduction which must be made because of the exemption of homesteads as required by Section 2406 et seq. of this Code.

Sixth: Compute the reduction in levy necessary to be made because of monies being required by law to be used for the purpose of reducing ad valorem tax levies.

The rates of levy for general fund, sinking fund, and other purposes authorized by law shall be separately made and stated, and the revenue accruing therefrom respectively, when collected, shall be credited to the proper fund accounts.