Okla. Stat. tit. 68, § 68-1905: Supplemental instruments or assignments of mortgages -

Procedure.

If subsequent to the recording of a mortgage on which all taxes,

if any, accrued under this article have been paid, a supplemental

instrument or mortgage is recorded for the purpose of correcting or

perfecting any recorded mortgage, or pursuant to some provision or

covenant therein, or an additional mortgage is recorded imposing the

lien thereof upon property not originally covered by or not

described in such recorded primary mortgage for the purpose of

securing the principal indebtedness which is, or under any

contingency may be, secured by such recorded primary mortgage, or an

assignment of mortgage is recorded, such supplemental instrument or

assignment of mortgage or mortgage shall not be subject to the tax

or fee levied and imposed by Section 1904 of this title unless it

creates or secures a new or further indebtedness or obligation other

than the principal indebtedness or obligation secured by or which

under any contingency may be secured by the recorded primary

mortgage, in which case a tax is levied on such new or further

indebtedness or obligation as heretofore provided in Section 1904 of

this title, and shall be paid to the county treasurer before the

time such instrument or additional mortgage is recorded. If, at the

time of recording such instrument, or additional mortgage, any

exemption is claimed under this section, there shall be filed with

the county treasurer and preserved in the office of the county

treasurer a statement under oath of the facts on which such claim

for exemption is based. The determination of the county treasurer

upon the question of exemption shall be reviewable on appeal to the

district court under the same procedure as appeals from the county

commissioners to the district court.