Okla. Stat. tit. 51, § 51-157: Denial of claim - Notice

A. A person may not initiate a suit against the state or a

political subdivision unless the claim has been denied in whole or

in part. A claim is deemed denied if the state or political

subdivision fails to approve the claim in its entirety within ninety

(90) days, unless the state or political subdivision has denied the

claim or reached a settlement with the claimant before the

expiration of that period. If the state or a political subdivision

approves or denies the claim in ninety (90) days or less, the state

or political subdivision shall give notice within five (5) days of

such action to the claimant at the address listed in the claim. If

the state or political subdivision fails to give the notice required

by this subsection, the period for commencement of an action in

subsection B of this section shall not begin until the expiration of

the ninety-day period for approval. The claimant and the state or

political subdivision may continue attempts to settle a claim,

however, settlement negotiations do not extend the date of denial

unless agreed to in writing by the claimant and the state or

political subdivision.

B. No action for any cause arising under this act, Section 151

et seq. of this title, shall be maintained unless valid notice has

been given and the action is commenced within one hundred eighty

(180) days after denial of the claim as set forth in this section.

The claimant and the state or political subdivision may agree in

writing to extend the time to commence an action for the purpose of

continuing to attempt settlement of the claim except no such

extension shall be for longer than two (2) years from the date of

the loss.