Fiduciary Income Tax

The Estate’s First-Year Playbook: Fiscal Years and the 645 Election

Two elections, both made at the very start of administration, decide how many returns an estate files and when beneficiaries pay tax. Executors who miss them file more returns, sooner, for no benefit.

Form 1041 Guide

Quick Answer

An estate may adopt a fiscal year ending the last day of any month within 12 months of death — chosen simply by filing the first Form 1041 on that year — which can defer beneficiaries’ K-1 income by up to a year. The section 645 election (Form 8855) folds the decedent’s revocable trust into the estate so both file one combined Form 1041 on that fiscal year. Trusts alone cannot do either: section 644 locks them to calendar years.

The fiscal year: deferral by calendar choice

Suppose someone dies in March 2026. A calendar-year estate files its first Form 1041 for March–December 2026, and beneficiaries who received distributions report that K-1 income on their 2026 returns. Choose a fiscal year ending February 28, 2027 instead, and the estate’s first year runs March 2026 through February 2027 — beneficiaries report the K-1 in their year containing February 2027, on returns filed in early 2028. Same income, same amounts, one full year of deferral, from nothing more than how the executor dated the first return. The mechanics of that timing rule are covered in the K-1 guide.

The 645 election: one return instead of two

Most modern estate plans center on a revocable living trust, which becomes a separate taxpayer the day the grantor dies — ordinarily a calendar-year taxpayer, per section 644, filing its own Form 1041 alongside the estate’s. The section 645 election erases that split: executor and trustee jointly elect on Form 8855 to treat the qualified revocable trust as part of the estate. The result is one combined Form 1041, on the estate’s fiscal year, with the estate’s other advantages (including the estate’s two-year exemption from estimated tax payments) covering the trust’s income too. For the common case — a funded living trust plus a modest probate estate — it is close to free money in saved filings and deferral.

Executor checklist, first ninety days

  1. Obtain the estate’s EIN (and the trust’s, if a 645 election is contemplated).
  2. Decide the tax year before the first Form 1041 goes in — the first filing adopts it.
  3. If a revocable trust exists, evaluate the 645 election with the trustee and calendar Form 8855’s due date (generally with the first combined return).
  4. Map the deadline: 15th day of the 4th month after the chosen year end, with a 5½-month extension available via Form 7004.

File the estate’s 1041 online

Prepare and e-file Form 1041 through the IRS MeF system with an electronic acknowledgment.

Start My Form 1041

Fiscal year & 645 FAQs

Can an estate choose its own tax year?
Yes — unlike trusts, which generally must use the calendar year under section 644, a decedent’s estate may adopt a fiscal year ending on the last day of any month within 12 months of death. The choice is made simply by filing the first Form 1041 on that year; no separate election form is required.
Why would an executor pick a fiscal year?
Two reasons. Deferral: beneficiaries report K-1 income in their tax year containing the estate’s year end, so a well-chosen fiscal year can push the first tax hit into the following calendar year. Administration: a fiscal year ending near the anniversary of death often lets the estate wrap its affairs in one or two returns instead of three short ones.
What is the section 645 election?
A joint election by the executor and the trustee of a qualified revocable trust — the decedent’s living trust — to treat the trust as part of the estate for income tax. The combined entity files one Form 1041, on the estate’s fiscal year if one was chosen, instead of the trust filing its own calendar-year return. The election is made on Form 8855, generally due with the first combined Form 1041.
How long does the 645 election last?
For an estate with no Form 706 requirement, until two years after the date of death. Where a 706 is required, until six months after the estate tax liability is finally determined. When the period ends, any continuing trust resumes life as a separate calendar-year taxpayer.
Does a fiscal year change the filing deadline?
The rule stays the same — Form 1041 is due the 15th day of the 4th month after the year ends — but the date moves with the year you chose. An estate with a fiscal year ending November 30 files by March 15, extendable 5½ months with Form 7004.

Disclaimer: Elections like the fiscal year and section 645 are consequential and fact-specific — make them with a qualified professional and the current IRS instructions in hand. This page is general information, not legal or tax advice. TaxFilingCenter is an IRS-authorized e-file provider and does not provide legal or tax advice.

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