§ 645. Certain revocable trusts treated as part of estate
(a)
General rule
For purposes of this subtitle, if both the executor (if any) of an estate and the trustee of a qualified revocable trust elect the treatment provided in this section, such trust shall be treated and taxed as part of such estate (and not as a separate trust) for all taxable years of the estate ending after the date of the decedent’s death and before the applicable date.
(b)
Definitions
For purposes of subsection (a)—
(c)
Election
The election under subsection (a) shall be made not later than the time prescribed for filing the return of tax imposed by this chapter for the first taxable year of the estate (determined with regard to extensions) and, once made, shall be irrevocable.