Okla. Stat. tit. 68, § 68-1906: Mortgages for indefinite amounts - Procedure

If the principal indebtedness secured or which by any

contingency may be secured by a mortgage is not determinable from

the terms of the mortgage, or if a mortgage is given to secure the

performance by the mortgagor, or of any other person of a contract

obligation other than the payment of a specific sum of money and the

maximum amount secured or which by any contingency may be secured by

the mortgage is not expressed therein, such mortgage shall be

taxable upon the value of the property covered by the mortgage,

which shall be determined by the county treasurer to whom such

mortgage is presented for taxation, unless at the time of presenting

such mortgage for taxation the owner thereof shall file with the

county treasurer a sworn statement of the maximum amount secured by

the mortgage. If such maximum amount is expressed in the mortgage

or in a sworn statement filed as required by this section, such

amount shall be the basis for assessing the tax levied by this

article. The statement filed by the owner of a mortgage pursuant to

this section shall thereafter at all times be binding upon and

conclusive against such owner, the holders of any bonds or

obligations secured by such mortgage and all persons claiming

through the mortgagee any interest in the mortgage or the mortgaged

premises. If the maximum amount secured or which by any contingency

may be secured by the mortgage is not expressed in the mortgage or

in a sworn statement so authorized by this section, the county

treasurer at the time such mortgage is offered for taxation may

require the mortgagor or mortgagee to furnish him with proofs as to

such facts as he deems necessary for the purpose of computing the

value of the property covered by the mortgage, and such proofs shall

be preserved in his office. His determination as to the basis for

computing the tax on such mortgage shall be subject to review on

appeal to the district court under the same procedure as cases

appealed from the county commissioners to the district court.