What Is the Section 645 Election: Benefits, Filing, and Duration

The Section 645 election lets the trustee of a revocable trust and the executor of the deceased grantor’s estate treat those two entities as one taxpayer for federal income tax purposes. Instead of filing a separate Form 1041 for the trust and another for the estate, the fiduciaries file a single combined Form 1041 and gain access to tax rules that apply to estates but not to standalone trusts. The election is made on IRS Form 8855, it must be filed by the due date (with extensions) of the estate’s first Form 1041, and once made it cannot be revoked.¹

Which Trusts Qualify

A trust qualifies if the decedent was treated as its owner for income tax purposes immediately before death because the decedent held the power to revoke it. The code calls this a qualified revocable trust, or QRT, and the test traces to Section 676, which treats any grantor who can take back trust property as the owner of that property.² Most standard revocable living trusts meet this test, because the grantor keeps full power to amend or revoke them during life.

The election also contemplates a “related estate,” meaning the decedent’s probate estate with an appointed executor. If the decedent held everything in the revocable trust and no probate estate was opened, the election is still available. In that case the QRT itself steps into the estate’s role for purposes of the election, and the trustee handles all filing responsibilities without an executor.³

If the decedent created more than one revocable trust, each one that independently meets the QRT definition can join. Fiduciaries can elect for some and leave others out. When multiple QRTs join and no executor has been appointed, one trustee has to be designated to file the combined Form 1041.³

How and When to File

The election is made on Form 8855, Election to Treat a Qualified Revocable Trust as Part of an Estate.⁴ Both the executor and the trustee sign. If no executor has been appointed, the trustee signs alone and indicates on the form that no executor exists and that the QRT is acting as the electing estate. When more than one QRT is joining, each trust must be separately identified on the form.

The deadline is the due date, including any extensions, of the first Form 1041 for the related estate. It applies even if the estate’s income for that first year is too low to otherwise trigger a filing requirement.³ There is no late-filing provision. Miss the deadline and the election is lost permanently. And once filed, it cannot be undone, so the choice deserves careful thought upfront.¹

The combined entity needs an Employer Identification Number before the first Form 1041 goes in. When an executor has been appointed, the combined entity usually uses the EIN already assigned to the probate estate. When the QRT is acting as the electing estate because no executor exists, the trustee has to obtain a new EIN for the combined entity.

Once the election takes effect, the QRT stops filing its own Form 1041 for the duration. All income, deductions, and credits from both the trust and the estate go on one return filed under the estate’s (or electing trust’s) EIN. The election is retroactive to the date of death, so the first combined return covers the period from the date of death through the end of the chosen tax year.

Why Make the Election

The payoff is access to tax rules that apply to estates but not to standalone non-grantor trusts. Individually some of these are small; together they can meaningfully reduce the tax burden during administration.

Fiscal Year Election

A non-grantor trust must use a calendar year ending December 31. An estate can pick any fiscal year ending on the last day of a month, and the combined entity under a Section 645 election inherits that flexibility. Choosing the right fiscal year-end can defer income recognition by up to eleven months, which matters when large asset sales or income distributions are expected shortly after death.

Higher Exemption

An estate gets a $600 deduction in place of a personal exemption. A simple trust gets $300 and a complex trust gets $100.⁵ The dollar difference is modest on any single return, but it reflects the broader principle that the combined entity gets the estate’s more favorable treatment across the board.

Estimated Tax Relief

An estate is exempt from making estimated income tax payments for any taxable year ending within two years of the decedent’s death.⁶ Without the election, the trust (now a non-grantor trust) would owe quarterly estimated payments from the start. The combined entity skips that obligation for its first two years, easing cash flow while assets are being gathered, appraised, and sold.

Charitable Deduction

The combined entity can take an unlimited charitable deduction under Section 642(c) for gross income paid to a qualifying charity, as long as the governing instrument authorizes the payment.⁵ The percentage-of-income limits that apply to individuals do not apply. The authorization requirement is the catch: a fiduciary cannot simply decide to donate and claim the deduction. The trust document or will has to authorize the payment.

Rental Real Estate

A decedent’s estate is treated as actively participating in rental real estate activities for tax years ending within two years of death, provided the decedent would have met the active participation requirement in the year of death. A QRT making the Section 645 election gets the same treatment and can use the rental real estate loss allowance that would otherwise require an active, living individual.⁷ Without the election, the trust falls under the standard passive activity rules for trusts, which are generally less favorable.

S Corporation Stock

This is where the election can prevent a serious problem. An estate can hold S corporation stock for the entire period of administration without jeopardizing the company’s S election. A trust that was a grantor trust before the owner’s death gets only a two-year window as an eligible S corporation shareholder after the owner dies.⁸ By treating the trust as part of the estate, the combined entity remains an eligible shareholder for the full election period, potentially years longer than the two-year trust window. Without the election, the trust would have to convert to a qualifying S corporation trust (such as a QSST or ESBT) or distribute the stock before that two-year deadline, or the company risks losing its S election entirely.

How Long the Election Lasts

The combined entity status is temporary. The length depends on whether a federal estate tax return (Form 706) is required.

No Form 706 required. The election period ends two years after the date of death. For decedents dying in 2026, a Form 706 is required only if the gross estate exceeds $15,000,000, so most estates fall below the threshold and use the two-year termination date.¹⁹
Form 706 required. The election period ends six months after the “final determination” of the estate tax liability. Final determination occurs when the IRS issues a closing letter, when the statute of limitations for assessment expires, or when any tax litigation is settled, whichever comes first. For complex estates or those under audit, this can extend well past two years.¹

What Happens After the Election Ends

On the day after the election period ends, the trust and the estate (if it still exists) become separate taxpayers again. The Form 1041 covering the year of termination includes the trust’s income and deductions only through the last day of the election period, along with a deduction for a deemed distribution of the trust’s share to the newly separate trust.¹⁰

The trust will generally need a new EIN going forward. If the estate continues after the election ends, it keeps its existing EIN. If there was no executor and the QRT had been acting as the estate, the trust must obtain a new EIN if it continues in existence.¹⁰ The trust then resumes filing its own Form 1041 as a non-grantor trust, with a calendar year and the lower trust exemption. Trustees who grew accustomed to the estate’s rules during the election period sometimes overlook this shift; the trust’s first standalone return after termination is where compliance errors tend to appear.

One more thing worth checking before filing Form 8855: state treatment. Not all states follow the federal Section 645 election, so even during the election period the trust and estate may need to file separate state fiduciary returns depending on where they sit. Confirm the position of the relevant state taxing authority before you make the federal election.

1
Office of the Law Revision Counsel. 26 USC 645 – Certain Revocable Trusts Treated as Part of Estate
2
Office of the Law Revision Counsel. 26 USC 676 – Power to Revoke
3
eCFR. 26 CFR 1.645-1 – Election by Certain Revocable Trusts to Be Treated as Part of Estate
4
Internal Revenue Service. About Form 8855
5
Office of the Law Revision Counsel. 26 USC 642 – Special Rules for Credits and Deductions
6
Office of the Law Revision Counsel. 26 USC 6654 – Failure by Individual to Pay Estimated Income Tax
7
Internal Revenue Service. Publication 925 (2025), Passive Activity and At-Risk Rules
8
Office of the Law Revision Counsel. 26 USC 1361 – S Corporation Defined
9
Internal Revenue Service. Frequently Asked Questions on Estate Taxes
10
GovInfo. 26 CFR 1.645-1 – Election by Certain Revocable Trusts to Be Treated as Part of Estate