Okla. Stat. tit. 68, § 68-223: Limitation of time for assessment of taxes - Extension

agreements - False or fraudulent or failure to file report or

return.

A. No assessment of any tax levied under the provisions of any

state tax law except as provided in this section, shall be made

after the expiration of three (3) years from the date the return was

required to be filed or the date the return was filed, whichever

period expires the later, and no proceedings by tax warrant or in

court without the previous assessment for the collection of such tax

shall be begun after the expiration of such period. No assessment

shall be required if a report or return, signed by the taxpayer, was

filed and the liability evidenced by the report or return has not

been paid. If the assessment has been made within the limitation

period set forth in this subsection, the tax may be collected by tax

warrant or court proceeding, but only if the tax warrant is issued

or the proceeding begun within ten (10) years after the assessment

of the tax has become final.

B. Where before the expiration of the time prescribed in

subsection A of this section for the assessment of the tax, both the

Tax Commission and the taxpayer have consented in writing to its

assessment after such time, the tax may be assessed at any time

prior to the expiration of the period agreed upon, and the period so

agreed upon may be extended by subsequent agreements in writing made

before the expiration of the period previously agreed upon. In

those instances where the time to file a claim for a refund has not

expired at the date the extension agreement is entered into, the

entering into such an agreement shall automatically extend the

period in which a refund may be allowed or a claim for a refund may

be filed to the final date of such agreement.

C. In the case of a false or fraudulent report or return, with

intent to evade tax, the tax may be assessed, or a proceeding in

court for collection of such tax may be begun without assessment, at

any time. The term “false or fraudulent” as used in this subsection

shall have the same meaning as when used in Section 6501 of the

Internal Revenue Code.

D. In the case of a willful attempt in any manner to defeat or

evade tax imposed by this title, the tax may be assessed, or a

proceeding in court for the collection of such tax may be begun

without assessment, at any time.

E. In the case of a failure to file a report or return, the tax

may be assessed, or a proceeding in court for the collection of such

tax may be begun without assessment, at any time.