Okla. Stat. tit. 68 § 1908
In the case of mortgages made by corporations in trust to secure payments of bonds or obligations issued or to be issued thereafter, if the total amount of principal indebtedness which under any contingency may be advanced or accrued, or which may become secured by any such mortgage which is subject to this article has not been advanced or secured thereon or become secured thereby before such mortgage is recorded, it may contain at the end thereof a statement of the amount which at the time of the execution and delivery thereof has been advanced or accrued thereon or which is then secured by such mortgage; thereupon the tax payable on the recording of the mortgage shall be computed on the basis of the amount so stated to have been so advanced or accrued thereon, or which is stated to be secured thereby. Such statement shall thereafter at all times be binding upon and conclusive against the mortgagee, the holders of any bonds or obligations secured by such mortgage and all persons claiming through the mortgagee any interest in the mortgage or in the mortgaged premises. Whenever a further amount is to be advanced under the original mortgage, or shall accrue thereon or become secured thereby, the corporation making such mortgage shall, at or before the time when such amount is to be advanced, accrues or becomes secured, file in the office of the county treasurer in the county where such mortgage has been or is first recorded, a statement, verified by the secretary, treasurer or other proper officer of said corporation of the amount of principal indebtedness to be so advanced, accruing or becoming secured, and the tax on such amount shall become due and payable at the time of filing such statement. Such additional tax shall be paid to the county treasurer in the county where such mortgage has been or is first recorded and a receipt therefor shall be noted in the margin of the record of such mortgage and if requested a duplicate receipt for such payment shall also be given to the party paying such tax and the note of such payment or additional payment or such receipt shall have the same force and effect as the record of receipt of the tax which under this article is payable at or before the recording of the mortgage. If such additional tax is not paid as required by this section, the trust mortgagee shall not certify any bond or other obligation issued on account thereof, and the district attorney of the county in which such mortgage has been or is first recorded may maintain an action against the corporation making such mortgage to recover the amount of such tax, with interest at the rate of one percent (1%) per month from the date when the same became due, and upon recovering such tax and interest such district attorney shall pay the same to the county treasurer of such county in satisfaction of such tax. The corporation making such mortgage or the owner of the property which secures the mortgage debt shall annually within thirty (30) days after July 1st, until the maximum amount of principal indebtedness secured by such mortgage has been advanced, has accrued or become secured and the tax thereon paid, file in the office of the county treasurer in the county where such mortgage has been or is first recorded, a statement, verified by the secretary, treasurer or other proper officer of said corporation, of the total amount of principal indebtedness that has been advanced or has accrued on such mortgage, or has become secured thereby, prior to the first day of July preceding the filing of such statement. A failure to file any statement required by this section within the time required shall subject the corporation making such mortgage to a penalty of One Hundred Dollars ($100.00) per day for each day such failure continues, recoverable by the district attorney of the county in which such mortgage has been or is first recorded. Provided, however, that where a mortgage, or deed of trust, is executed to secure the payment of bonds issued by any domestic railroad, transportation, transmission or industrial corporation and the money derived from the sale of said bonds so secured by said mortgage, or deed of trust, is to be used for the creation, construction, building, improving and erecting of property that will be subject to an ad valorem tax in the county where same is situated, there shall be paid a recording fee on said mortgage, or deed of trust, so executed for recording said mortgage, or deed of trust, the sum of twenty-five cents ($0.25) for first folio and ten cents ($0.10) for each additional folio and fifty cents ($0.50) for indexing and recorder's certificate instead of the fees designated in this article, and on payment of same shall not be subject to the penalties prescribed in this article.
Okla. Stat. tit. 68, § 1908