26 U.S.C. § 645 — Certain revocable trusts treated as part of estate

(a) General rule. For this subtitle, if both the executor, if there is one, of an estate and the trustee of a qualified revocable trust elect the treatment provided here, the trust is treated and taxed as part of the estate, not as a separate trust, for all taxable years of the estate that end after the decedent’s death and before the applicable date. (b) Definitions. For subsection (a): (1) “Qualified revocable trust” means any trust, or portion of a trust, that was treated under section 676 as owned by the decedent of the estate referred to in subsection (a) because of a power in the grantor. The grantor’s power is determined without regard to section 672(e). (2) “Applicable date” means (A) if no return of tax imposed by chapter 11 must be filed, the date 2 years after the decedent’s death; or (B) if such a return must be filed, the date 6 months after the final determination of the liability for tax imposed by chapter 11. (c) Election. The election under subsection (a) must be made no later than the deadline for filing the estate’s return of tax imposed by this chapter for the first taxable year of the estate, with extensions taken into account. Once made, the election cannot be revoked.