Okla. Stat. tit. 60, § 60-753: Time for filing disclaimer

Such disclaimer shall be filed at any time after the creation of

the interest, but in all events within nine (9) months after the

effective date of the nontestamentary instrument creating the

interest, or, if the disclaimant is not then finally ascertained as

a beneficiary or his interest has not then become indefeasibly fixed

both in quality and in quantity, such disclaimer shall be filed not

later than nine (9) months after the event which would cause him so

to become finally ascertained and his interest to become

indefeasibly fixed both in quality and quantity. With respect to a

disclaimer, an interest which is a joint tenancy interest in

property shall not be considered to be indefeasibly fixed both in

quality and quantity until the death of all but one of the persons

owning such joint tenancy interest.