IRC § 645 Election: How to Treat a Revocable Trust as Part of the Estate for Income Taxes

When a settlor dies, their revocable living trust becomes irrevocable — and begins facing some of the worst tax brackets in the code. The § 645 election gives newly-named trustees an option most CPAs know but many trustees don't hear about: temporarily treat the trust as part of the estate, unlocking fiscal year flexibility, exemption from quarterly estimated taxes, and the ability to pool estate deductions against trust income. There is a hard deadline. Missing it forfeits the option permanently.

What is a qualified revocable trust (QRT)?

A trust qualifies for the § 645 election if it was treated as owned by the decedent under IRC § 676 — the power to revoke — immediately before death.¹ In practice, this means a standard revocable living trust where the settlor retained the right to amend or revoke the trust at any time during life. This is the most common type of living trust.

The key requirement is that the trust was a grantor trust under § 676 the instant before death. Irrevocable trusts (ILITs, GRATs, SLATs, SNTs) do not qualify. A trust that became irrevocable during the settlor's lifetime — for example, an irrevocable asset protection trust created years earlier — does not qualify, even if the same person created it.

Most successor trustees administering a deceased parent's living trust are administering a QRT.

How the election works

When the § 645 election is in effect, the trust and the related estate are treated as a single entity for federal income tax purposes during the election period.² The combined entity:

• Files one Form 1041 (the estate's return, not a separate trust return)
• Can elect a fiscal year ending in any month
• Uses the estate's $600 exemption instead of the trust's $300 or $100
• Is exempt from estimated tax payments for the first two years after the decedent's death
• Can apply estate deductions — administrative expenses, losses — against trust income within the combined entity

When the election period ends, the trust begins filing its own separate Form 1041 on a calendar year, subject to all normal trust rules.

Who files Form 8855: Both the trustee of the QRT and the executor of the related estate must sign and file Form 8855. If there is no executor — because the decedent's estate passed entirely through the trust and beneficiary designations without triggering formal probate — the trustee alone makes the election and acts as executor for this purpose.³

The four benefits that drive most elections

1. Fiscal year election — income deferral and filing flexibility

Trusts must use a calendar year. Estates can elect any fiscal year ending on the last day of any month.⁴ The § 645 election allows the combined trust/estate entity to adopt the estate's fiscal year, creating two advantages:

Longer first tax year: If a settlor dies in July 2026 and the estate elects a June 30 fiscal year, the first combined return covers July 2026 through June 30, 2027 — nearly a full year. Without the election, a calendar-year trust would file a short-year return for July–December 2026 in early 2027. This timing can matter when the estate holds concentrated positions or real estate generating significant income.

Income deferral: Income earned in, say, November 2026 that falls into a fiscal year ending June 30, 2027 is not taxable until the return for that fiscal year is filed (and paid) in late 2027 at the earliest — up to a year of deferral. The beneficiaries who receive K-1s similarly defer recognizing that income.

Practical tradeoff: A non-calendar fiscal year adds complexity — K-1s issued on a non-December schedule can confuse beneficiaries preparing their individual returns. Most trustees choose a fiscal year based on when the decedent died: if death was in the first half of the year, a December 31 fiscal year (or a September 30 or October 31) may provide meaningful deferral; if death was late in the year, the deferral benefit from a non-calendar year is larger.

2. Exemption from estimated tax payments

A trust that begins accumulating income must make quarterly estimated tax payments to the IRS.⁵ For a calendar-year trust created at a parent's death in 2026, estimated payments would begin immediately — April, June, September of 2026 — even though the trust may not have organized its accounts, obtained an EIN, or engaged a CPA yet.

Estates are exempt from estimated tax payments for the first two years after the decedent's death.⁵ A QRT making the § 645 election is treated as part of the estate during the election period, which is typically two years — meaning the combined entity owes no estimated payments through the election period. This simplifies cash flow management during trust administration and removes one penalty exposure for newly-named trustees who are still getting organized in the first months.

Important: The tax itself is still owed; it is due with the annual Form 1041. The exemption only eliminates the quarterly payment obligation.

3. Higher exemption amount

Every trust and estate receives a personal exemption before computing taxable income:

• Simple trust: $300⁶
• Complex trust: $100⁶
• Estate: $600⁶

During the § 645 election period, the combined entity uses the $600 estate exemption. The absolute dollar difference is modest — at most a few hundred dollars of tax. But it is a small, automatic benefit that comes at no additional cost.

4. Pooling estate deductions against trust income

Estates often incur significant administrative expenses in the first year: attorney fees, executor fees, appraisal costs, selling expenses for real property. Under the § 645 election, these estate-level deductions flow through the combined Form 1041 and can offset trust investment income.

Without the election, trust deductions and estate deductions are separate — neither can offset the other's income. With it, an estate that has $50,000 of deductible administrative expenses in year one can directly reduce the trust's taxable income dollar-for-dollar. At the 37% bracket, that is $18,500 in federal tax savings.⁷

This benefit is most significant when the estate has large, deductible legal or administrative costs — for example, an estate that must probate real property, litigate a will contest, or handle a complex business interest.

The election period: how long does it last?

The § 645 election period ends at the earliest of:²

1. The day the combined trust and estate have distributed all their assets (i.e., administration is complete), OR
2. Two years after the date of the decedent's death (if no federal estate tax return, Form 706, was required), OR
3. Six months after the date of final determination of the estate tax liability (if Form 706 was filed)

For most revocable trusts below the $15M federal estate tax exemption — the permanent OBBBA threshold effective 2026 — no Form 706 is required, and the election period runs for two full years from the date of death.

After the election period, the trust reverts to filing its own calendar-year Form 1041 as a separate non-grantor trust, subject to normal estimated tax requirements and the $100 or $300 exemption.

The filing deadline: hard, no relief

Form 8855 must be filed by the due date — including any valid extension — of the first Form 1041 for either the estate or the qualified revocable trust, whichever is filed first.³

For a decedent who died in 2026, the trust's first calendar-year Form 1041 covers the period from date of death through December 31, 2026. That return is due April 15, 2027, or September 30, 2027 with a 5.5-month extension (Form 7004). Form 8855 must be filed by that same extended date.

There is no provision for late elections. The IRS does not grant relief for missed § 645 elections under the normal automatic or discretionary procedures.⁸ A trustee who fails to file Form 8855 by the extended due date of the first Form 1041 permanently forfeits this option. Once the first trust return is filed without the election, the filing closes.

Practical implication: This decision should be made as part of first-year tax planning — ideally before the first Form 1041 is filed, and certainly before that return goes on extension. A CPA engaged in the first few months after the settlor's death can evaluate the election and file Form 8855 at the same time as the first return or extension.

When does the § 645 election make the most sense?

The election is not always beneficial. Work through these factors:

Election usually makes sense when:

• The trust will accumulate significant income during administration (large investment portfolio, rental real estate, business interest distributions)
• The estate has substantial deductible administrative expenses that can offset trust income
• The decedent died early in the calendar year, making fiscal-year deferral meaningful
• There is no executor and the trustee wants the flexibility to choose a fiscal year
• Trustees want to avoid organizing quarterly estimated payments during the chaotic first months of administration

Election may not be worth the complexity when:

• The trust will distribute substantially all income to beneficiaries promptly — distributions carry out DNI to beneficiaries who pay tax at their own rates regardless of whether an election is made
• Administration will be brief (under 12 months) — the deferral and estimated tax benefits may not justify the added CPA complexity of a fiscal year return
• Trust income is primarily tax-exempt municipal bond interest — the compressed bracket problem is less severe if most income is already exempt
• The estate has few deductible expenses — the pooling benefit does not exist

The fee-only advisor's role here is modeling the numbers: how much income will the trust accumulate over the administration period, what is the character of that income, what are the estate's deductions, and what does the tax comparison look like over the election period? That model usually takes an hour and can identify tens of thousands of dollars in tax differences between making and not making the election.

What happens after the election period ends?

When the § 645 election period expires:

• The trust begins filing its own calendar-year Form 1041 as a non-grantor trust
• The trust must begin making quarterly estimated tax payments if it expects to owe $1,000 or more
• The trust's exemption reverts to $100 (complex) or $300 (simple)
• Any unused deductions or net operating losses from the combined entity can be carried out to the trust under § 642(h)
• The trust adopts its own separate EIN (or uses the EIN previously obtained at the settlor's death — the same EIN continues)

The transition requires a "short-period" trust return to cover the gap between the end of the estate's fiscal year and the start of the trust's first full calendar year. This should be anticipated in tax planning during the election period.

Interaction with other post-death elections

The § 645 election interacts with several other time-sensitive decisions the trustee and executor face:

• 65-day election (IRC § 663(b)): Still available during the § 645 election period. Distributions within the first 65 days of the new fiscal year can be applied against the prior fiscal year's DNI. Both elections can be used simultaneously.
• Alternate valuation date (IRC § 2032): An estate tax election, available only if Form 706 is required. Independent of the § 645 election.
• Portability election: A Form 706 election for the surviving spouse's DSUE. Must be filed within 9 months (5-year extension available under Rev. Proc. 2022-32 if gross estate below the filing threshold). Independent of § 645.
• Fiscal year for charitable remainder trusts: CRTs are not QRTs and have their own tax regime — the § 645 election does not apply.

How a fee-only advisor helps with this decision

The § 645 election is a CPA decision — the trustee cannot make it effectively without a tax preparer with fiduciary experience. But the financial modeling that informs the decision is an advisor function:

• Income projection: Estimating how much income the trust will accumulate vs. distribute during the administration period, and what the tax impact is at trust vs. estate rates
• Distribution modeling: Deciding how aggressively to distribute income to beneficiaries (which reduces the tax pressure that the § 645 election is meant to address)
• Investment policy during administration: A trust in administration should typically hold lower-yielding, more liquid assets than a long-term trust — this reduces the income that would face compressed brackets regardless of the election decision
• Coordination between advisor, CPA, and attorney: The trustee should not be managing these three professionals independently. A fee-only advisor who has worked with trustees coordinates the filing calendar, ensures the § 645 election is evaluated before the first return is filed, and documents the process as part of the trustee's prudent-investor record

Sources

1. IRC § 645 — Certain revocable trusts treated as part of estate. Defines qualified revocable trust, election mechanics, and election period rules.
2. 26 CFR § 1.645-1 — Election by certain revocable trusts to be treated as part of estate. Final regulations covering QRT definition, election procedure, election period duration, and post-election treatment. LII / Cornell Law School.
3. IRS — About Form 8855, Election to Treat a Qualified Revocable Trust as Part of an Estate. Filing instructions, due date (first Form 1041 including extensions), who must sign, no-late-election rule.
4. IRS — Forms 1041 and 1041-A: When to File. Fiscal year rules for estates; calendar year requirement for trusts; extension via Form 7004.
5. IRS Form 1041-ES (2026) — Estimated Income Tax for Estates and Trusts. Two-year estimated tax exemption for estates; quarterly payment requirements for trusts. 2026 tax rate schedule per IRS Rev. Proc. 2025-32.
6. IRC § 642(b) — Deductions for Personal Exemptions. Statutory exemption amounts: $300 simple trust, $100 complex trust, $600 estate. Not adjusted for inflation.
7. The Tax Adviser — The Sec. 645 election to treat a trust as part of the estate (May 2024). Pooling of deductions, practical benefits analysis, interaction with other post-mortem elections.
8. Greenleaf Trust — Why Make the IRC 645 Election. No-relief rule for late elections; practical planning considerations; when election benefits outweigh complexity.

This guide covers federal income tax rules. State income tax treatment of the § 645 election varies — some states conform, others do not. Consult a CPA with fiduciary tax experience for state-specific guidance. Tax values verified against 2026 IRS Rev. Proc. 2025-32. Estate tax exemption reflects OBBBA (July 2025), which permanently set the federal exemption at $15M.