PROB §279: (a) A disclaimer to be effective shall be filed within a reasonable time after the person able to disclaim acquires knowledge of the interest.

(a) A disclaimer to be effective shall be filed within a reasonable time after the person able to disclaim acquires knowledge of the interest. (b) In the case of any of the following interests, a disclaimer is conclusively presumed to have been filed within a reasonable time if it is filed within nine months after the death of the creator of the interest or within nine months after the interest becomes indefeasibly vested, whichever occurs later: (1) An interest created under a will. (2) An interest created by intestate succession. (3) An interest created pursuant to the exercise or nonexercise of a testamentary power of appointment. (4) An interest created by surviving the death of a depositor of a Totten trust account or P.O.D. account. (5) An interest created under a life insurance or annuity contract. (6) An interest created by surviving the death of another joint tenant. (7) An interest created under an employee benefit plan. (8) An interest created under an individual retirement account, annuity, or bond. (9) An interest created under a transfer on death beneficiary designation in a deed or other instrument. (c) In the case of an interest created by a living trust, an interest created by the exercise of a presently exercisable power of appointment, an outright inter vivos gift, a power of appointment, or an interest created or increased by succession to a disclaimed interest, a disclaimer is conclusively presumed to have been filed within a reasonable time if it is filed within nine months after whichever of the following times occurs latest: (1) The time of the creation of the trust, the exercise of the power of appointment, the making of the gift, the creation of the power of appointment, or the disclaimer of the disclaimed property. (2) The time the first knowledge of the interest is acquired by the person able to disclaim. (3) The time the interest becomes indefeasibly vested. (d) In case of an interest not described in subdivision (b) or (c), a disclaimer is conclusively presumed to have been filed within a reasonable time if it is filed within nine months after whichever of the following times occurs later: (1) The time the first knowledge of the interest is acquired by the person able to disclaim. (2) The time the interest becomes indefeasibly vested. (e) In the case of a future estate, a disclaimer is conclusively presumed to have been filed within a reasonable time if it is filed within whichever of the following times occurs later: (1) Nine months after the time the interest becomes an estate in possession. (2) The time specified in subdivision (b), (c), or (d), whichever is applicable. (f) If the disclaimer is not filed within the time provided in subdivision (b), (c), (d), or (e), the disclaimant has the burden of establishing that the disclaimer was filed within a reasonable time after the disclaimant acquired knowledge of the interest.