Form 706 Estate Tax Return, Portability, and DSUE: Executor and Practitioner Guide

Form 706 (United States Estate and Generation-Skipping Transfer Tax Return) is one of the most consequential returns in estate and gift tax practice. Filing it when not strictly required by income -- or failing to file it when it could preserve a surviving spouse's exclusion -- can have a permanent and substantial tax impact. OBBBA permanently set the basic exclusion amount at a higher level, eliminating the prior-law sunset that would have cut the exclusion roughly in half after December 31, 2025. The combination of a large permanent exclusion and the portability election means that estate planning now turns as much on executor conduct (filing Form 706, making the portability election, allocating GST exemption) as on the size of the decedent's estate.

This guide is written for enrolled agents, CPAs, and tax attorneys who advise executors, surviving spouses, and estate planning clients. It covers: the federal estate tax and Form 706 filing requirement; the portability election and DSUE mechanics; the Rev. Proc. 2022-32 late portability window and its December 31, 2026 hard deadline for estates of decedents dying on or before December 31, 2021; the GST exemption's non-portability; the last deceased spouse rule; key Form 706 schedules; the marital deduction and QTIP trusts; and the basis step-up under IRC 1014. All dollar amounts, thresholds, and rates: verify at IRS.gov before use in client engagements. OBBBA provisions are recently enacted; final regulations and IRS guidance govern. This guide is informational and does not constitute legal or tax advice. For OBBBA changes to the pass-through deduction, see the Section 199A QBI Deduction OBBBA Practitioner Guide; for OBBBA pass-through entity tax election mechanics, see the PTET Election and OBBBA Guide.

Section 1: The Federal Estate Tax and Form 706 Filing Requirement

IRC 2001: the estate tax

IRC 2001 imposes a tax on the transfer of the taxable estate of every U.S. citizen and resident. The taxable estate is the gross estate (the value of all property the decedent owned or had an interest in at death, per IRC 2031-2046) minus allowable deductions (funeral expenses, debts, the marital deduction, the charitable deduction, and others per IRC 2053-2056). The applicable credit amount offsets the tentative estate tax; the amount of the credit effectively equals the tax on the basic exclusion amount, which means estates at or below the applicable exclusion amount owe no estate tax.

Form 706 filing requirement

Form 706 is required if the gross estate plus adjusted taxable gifts (taxable gifts made after December 31, 1976) exceeds the applicable exclusion amount under IRC 2010. The specific filing threshold: verify at IRS.gov and IRC 2010 for the applicable tax year. An estate that falls below the filing threshold is not required to file Form 706 for estate tax liability purposes -- but may still need to file to make the portability election (Section 2, below).

OBBBA: permanent exclusion, no sunset

Under prior law (the Tax Cuts and Jobs Act, TCJA), the basic exclusion amount was substantially increased but was subject to a sunset on December 31, 2025, after which it would have returned to approximately half the TCJA amount. OBBBA permanently set the basic exclusion amount at the enhanced level, eliminating the sunset cliff. For decedents dying in 2026 and later, the exclusion is permanent law at the current basic exclusion amount per IRS.gov (adjusted annually for inflation under OBBBA). OBBBA is recently enacted and subject to ongoing regulatory interpretation and IRS guidance; verify the current applicable exclusion amount at IRS.gov before advising clients.

The elimination of the sunset removes the planning cliff that had driven urgency in prior years to make large lifetime gifts before December 31, 2025. However, it does not reduce the urgency of the Rev. Proc. 2022-32 portability election for estates of decedents dying on or before December 31, 2021 -- that deadline remains December 31, 2026. For the broader OBBBA context across individual and pass-through taxation, see the Section 199A QBI OBBBA Practitioner Guide.

Filing deadline and extension

Form 706 is due nine months after the decedent's date of death. An automatic six-month extension of time to file (not to pay) is available by filing Form 4768 (Application for Extension of Time to File a Return and/or Pay U.S. Estate Taxes) before the nine-month deadline. Note: under Rev. Proc. 2022-32 (Section 3, below), the five-year late portability window replaces the standard nine-month deadline for below-threshold estates seeking only to make the portability election.

Who files Form 706

The executor or personal representative of the estate files Form 706 and signs it under penalties of perjury. If the estate has no court-appointed executor, a person in actual or constructive possession of the decedent's property may be required to file as the executor (under IRC 2203's definition of executor). For Rev. Proc. 2022-32 late portability filings where the estate has been closed, the surviving spouse or the surviving spouse's executor (if the surviving spouse has since died) may be able to file Form 706. Verify the filing authority rules at IRS.gov and in the current Form 706 instructions.

Section 2: Portability and the DSUE

What portability means

Portability, enacted under IRC 2010(c), allows the surviving spouse to use the unused portion of the first-to-die spouse's basic exclusion amount. This unused amount is the Deceased Spousal Unused Exclusion (DSUE). Before portability was enacted, any unused exclusion from the first spouse's death was permanently forfeited. Portability makes it possible for a married couple to effectively combine their exclusion amounts, even if the first spouse's estate was not large enough to use the full exclusion.

DSUE: the amount and how it is fixed

The DSUE is the amount of the first-to-die spouse's applicable exclusion amount that was not applied against the first spouse's taxable estate. The DSUE is determined and fixed as of the date of the first spouse's death. It does not increase for subsequent inflation adjustments, and it does not increase if the surviving spouse's estate (or the DSUE itself) appreciates in value between the first spouse's death and when the surviving spouse uses the DSUE. The DSUE amount calculation mechanics: hedge to IRS.gov and the current Form 706 instructions for the precise formula. The surviving spouse may use the DSUE during life (against taxable gifts) and at death (against the surviving spouse's taxable estate).

How to elect portability

The executor of the first-to-die spouse's estate must file Form 706 and indicate the portability election. No separate election form or statement is required; filing a complete and timely Form 706 constitutes the election. Importantly, Form 706 must be filed to elect portability even if the estate is below the filing threshold -- meaning even if no estate tax is owed and the estate would not otherwise be required to file Form 706. The election is made on Form 706 itself.

Section 3: Rev. Proc. 2022-32 and the Late Portability Election Window

What Rev. Proc. 2022-32 provides

Rev. Proc. 2022-32 provides a simplified method for the estate of a decedent to make a portability election on a late-filed Form 706, without applying for a private letter ruling or going through the full extension request process. The procedure is available only for estates whose gross estate does not exceed the applicable exclusion amount at the time of death -- that is, estates that were not required to file Form 706 for estate tax liability purposes but that failed to file a timely Form 706 to elect portability.

How to file under Rev. Proc. 2022-32

File Form 706 on or before the earlier of: (a) the fifth anniversary of the decedent's date of death, or (b) the date on which the statute of limitations on assessment of estate tax expires for the decedent's estate. At the top of Form 706, include the notation:

FILED PURSUANT TO REV. PROC. 2022-32 TO ELECT PORTABILITY UNDER IRC 2010(c)(5)(A)

Verify the full filing mechanics, required attachments, and applicable instructions in the current Form 706 and instructions on IRS.gov. The Rev. Proc. 2022-32 procedure does not require the estate to pay estate tax or include estate tax calculations for an estate that is below the filing threshold; it is filed solely to preserve the portability election.

The December 31, 2026 hard deadline

For decedents who died on or before December 31, 2021, the fifth anniversary of the date of death falls on or before December 31, 2026. This means the Rev. Proc. 2022-32 late portability window closes December 31, 2026, for all such estates. The deadline is not extendable. There is no Form 4768 extension available for the Rev. Proc. 2022-32 window. After December 31, 2026, estates of decedents dying on or before December 31, 2021 that have not filed Form 706 are permanently foreclosed from making the portability election.

Practitioners with surviving spouse clients should check the client file immediately. The relevant question: did the first-to-die spouse die on or before December 31, 2021, and was a Form 706 filed? If the answer is "died on or before December 31, 2021" and "no Form 706 was filed," the practitioner must advise the client and prepare the late Form 706 under Rev. Proc. 2022-32 before December 31, 2026. Allow 60-90 days for preparation; do not wait until late in 2026.

Post-December 31, 2026: estates of decedents dying after December 31, 2021

Surviving spouses of decedents who died after December 31, 2021 have their own five-year window from the date of the decedent's death to file a late Form 706 under Rev. Proc. 2022-32. The December 31, 2026 hard deadline applies only to decedents dying on or before December 31, 2021. Practitioners should calendar five-year deadlines for each client whose first-to-die spouse did not file a timely Form 706.

Section 4: GST Exemption -- NOT Portable

What this means in practice

Estate planners frequently overlook this distinction. A portability election filed under Rev. Proc. 2022-32 or via a timely Form 706 preserves the DSUE for estate tax and gift tax purposes (IRC 2010) but does nothing for the deceased spouse's unused GST exemption. The GST exemption is a separate tax attribute allocated per taxpayer; each individual has their own GST exemption, and unused portions do not transfer to the surviving spouse at death.

If the deceased spouse had a GST exemption that was not allocated during life (on gift tax returns) or at death (on Form 706, Schedule R), that exemption is permanently lost at the deceased spouse's death. No amount of portability planning, no late Form 706, and no administrative procedure can recover an unallocated GST exemption after the fact.

How to preserve GST exemption

Proper allocation of the GST exemption is accomplished: during life on gift tax returns (Form 709) when making generation-skipping transfers; and at death through the decedent's Form 706, Schedule R (for direct skips and taxable terminations) and the related schedules. The allocation mechanics for Schedule R and the GST inclusion ratio computation: verify in the current Form 706 instructions on IRS.gov. Practitioners who file a Form 706 solely for portability under Rev. Proc. 2022-32 should also address Schedule R -- a late Rev. Proc. 2022-32 Form 706 may be the last opportunity to make an automatic allocation of GST exemption or to elect out of automatic allocation for certain trusts. For the lifetime side of GST planning, including Schedule C allocation under IRC 2632 and gift-splitting mechanics, see our Form 709 gift tax and GST allocation guide.

Section 5: The Last Deceased Spouse Rule

The rule

Under IRC 2010(c)(4), the DSUE is available only from the most recently deceased spouse. A surviving spouse may have been widowed more than once. If the surviving spouse has remarried and the second spouse dies before the surviving spouse, the DSUE from the first deceased spouse is replaced by any DSUE from the second deceased spouse. The first deceased spouse's DSUE is permanently lost, regardless of how large it was.

The worst-case scenario

Consider a surviving spouse who was widowed with a large DSUE from the first spouse. The surviving spouse remarries. The second spouse dies first, having used all or most of the second spouse's applicable exclusion amount during life or in a large estate. In this scenario, the surviving spouse has lost the DSUE from the first spouse (replaced by the second spouse's DSUE upon the second spouse's death) and the second spouse's DSUE may be zero or very small. The surviving spouse may end up with no DSUE, despite the first spouse having had a substantial unused exclusion.

Planning implications for remarriage

Surviving spouses considering remarriage should understand the DSUE risk before remarrying. One planning strategy is to use the DSUE from the first deceased spouse (through taxable gifts) before remarrying, thereby "locking in" the benefit of the first spouse's DSUE before it is potentially replaced or lost. Whether this gifting strategy makes sense depends on each client's facts, projected estate, gift tax consequences, and the size of the DSUE relative to the expected estate. Hedge this analysis to estate planning counsel; the interaction of gift planning, the DSUE, and the last deceased spouse rule is a fact-specific determination.

Section 6: Form 706 Content and Key Schedules

The current Form 706 (Rev. August 2025) and accompanying instructions are available on IRS.gov. Verify the current version and instructions before beginning any Form 706 engagement. Form 706 is extensive. Allow 60-90 days for preparation; for late Rev. Proc. 2022-32 filings, begin immediately given the December 31, 2026 deadline for decedents dying on or before December 31, 2021.

Section 7: Marital Deduction and QTIP Trusts

The unlimited marital deduction (IRC 2056)

IRC 2056 provides an unlimited marital deduction for property passing from a decedent to a surviving spouse who is a U.S. citizen. "Unlimited" means there is no cap; assets passing outright to a U.S. citizen surviving spouse are fully deductible from the gross estate. The marital deduction defers the estate tax to the surviving spouse's death, when the combined estate (the original assets plus any DSUE portability) is subject to tax. The marital deduction is a deferral mechanism, not a permanent exclusion; proper portability planning ensures the surviving spouse has the maximum available exclusion when the deferred estate tax obligation comes due. Do not state specific marital deduction amounts; verify current deduction limits and qualifying transfer requirements at IRS.gov.

QTIP trusts

A Qualified Terminable Interest Property (QTIP) trust allows a decedent to leave assets in trust for a surviving spouse while controlling the ultimate disposition of the remaining trust assets (typically to the decedent's children or other beneficiaries, rather than the surviving spouse's beneficiaries on remarriage). A QTIP trust qualifies for the marital deduction if: (a) the surviving spouse receives all income from the trust at least annually, and (b) the executor makes the QTIP election on Schedule M of Form 706. No other qualifying interest (such as the right to invade principal) is required to qualify for the QTIP election; income rights are sufficient.

QTIP and portability: the planning tension

A QTIP election reduces the decedent's taxable estate by the value of the property transferred to the QTIP trust. A smaller taxable estate means a larger unused exclusion -- which means a larger potential DSUE for portability. However, the DSUE is fixed at the date of the first spouse's death; any subsequent growth in the QTIP trust assets does not increase the DSUE. The planning tension arises because maximizing the QTIP election maximizes the marital deduction and the DSUE, while also deferring tax on all transferred assets to the surviving spouse's estate. Proper estate planning must analyze both the DSUE portability value and the long-term estate tax exposure on the surviving spouse's side when recommending the size of the QTIP election. These decisions are fact-specific and should be made with qualified estate planning counsel.

Noncitizen surviving spouses: QDOT requirement

The unlimited marital deduction is NOT available for assets passing to a surviving spouse who is not a U.S. citizen. For a noncitizen surviving spouse, the marital deduction requires that the assets pass into a Qualified Domestic Trust (QDOT) that meets the requirements of IRC 2056A. The QDOT requirement exists because a noncitizen surviving spouse could leave the United States before the deferred estate tax is collected. QDOT administration and distribution rules are distinct from QTIP rules; verify QDOT mechanics under IRC 2056A and the applicable Treasury Regulations.

Section 8: Basis Step-Up Under IRC 1014

The step-up: what it is and how it works

Under IRC 1014, the income tax basis of assets included in a decedent's gross estate is stepped up to the fair market value (FMV) of those assets as of the date of death (or the alternate valuation date, if that election is available and made). The step-up eliminates the capital gains tax that would otherwise be owed on appreciation that occurred during the decedent's lifetime. For example, an asset purchased for a low basis and held until death receives a new basis equal to its date-of-death FMV; a beneficiary who sells the asset immediately after death pays no capital gains tax on the pre-death appreciation.

Scope of the step-up in a married couple's estate

At the first spouse's death, only the decedent's assets (or the decedent's proportionate share of jointly held assets) receive the step-up. The surviving spouse's separately owned assets do NOT receive a step-up in basis at the first spouse's death; they will receive a step-up only when the surviving spouse dies. For jointly held property (joint tenancy with right of survivorship between spouses), only one-half of the joint property is included in the decedent's gross estate, and only that half receives the step-up.

Community property: a more favorable rule

In community property states, IRC 1014(b)(6) provides that ALL community property receives a step-up in basis at the first spouse's death -- including the surviving spouse's one-half share. This is more favorable than the common law rule (which steps up only the decedent's half of jointly held property). The community property step-up is a significant planning advantage; clients moving from common law states to community property states (or holding community property assets) should understand this rule. Verify the applicable state community property law and the federal tax treatment under IRC 1014(b)(6) before advising clients.

Portability and basis step-up are independent benefits

Portability (the DSUE) and the basis step-up under IRC 1014 are independent and distinct benefits. They arise from different code sections, they address different taxes (estate tax versus income tax), and they do not offset or substitute for each other. An estate below the estate tax filing threshold can still have significant income tax basis step-up benefits for appreciated assets. Conversely, a large estate with a substantial estate tax obligation can also have basis step-up planning implications for specific assets. Do not conflate the two. Both should be addressed in the estate plan and in the Form 706 preparation.

Section 9: Practitioner Checklist

Work through these steps in order for every estate engagement involving a surviving spouse. The first three items are time-sensitive and must be completed before December 31, 2026, for applicable estates.

Immediate action items (before December 31, 2026)

• Identify all surviving spouse clients whose spouse died on or before December 31, 2021 and who did NOT file a timely Form 706. This is the Rev. Proc. 2022-32 window. No Form 706 means no portability election; no portability election means the DSUE is permanently forfeited after December 31, 2026.
• Advise affected clients of the December 31, 2026 hard deadline. Rev. Proc. 2022-32 filings must be received by the IRS on or before December 31, 2026 for decedents dying on or before December 31, 2021. Begin preparation immediately; allow 60-90 days.
• Confirm executor or personal representative availability. If the estate has been closed and no executor is available, determine whether the surviving spouse or the surviving spouse's legal representative can file as executor for Rev. Proc. 2022-32 purposes. Verify authority under the current Form 706 instructions and IRC 2203.

Form 706 preparation checklist

• Determine gross estate value versus the filing threshold. Verify the applicable exclusion amount at IRS.gov for the decedent's year of death. If the gross estate plus adjusted taxable gifts exceeds the threshold, Form 706 is required. If below, Form 706 may still be filed to elect portability.
• Gather all asset valuations as of the decedent's date of death. Obtain qualified appraisals for real estate and other non-publicly-traded assets. Document the FMV basis for each asset on each schedule of Form 706.
• Prepare Form 706 (Rev. August 2025) or the current version on IRS.gov. For Rev. Proc. 2022-32 late filings, include the notation "FILED PURSUANT TO REV. PROC. 2022-32 TO ELECT PORTABILITY UNDER IRC 2010(c)(5)(A)" at the top of the return.
• Complete and review Schedule M (marital deduction and QTIP election). Determine whether to make the QTIP election and, if so, for what amount. Model the effect of the QTIP election on the DSUE available for portability before finalizing.
• Complete Schedule R (GST exemption allocation). Separately address the GST exemption. Do NOT assume the GST exemption is portable; it is not. Determine whether automatic allocation applies to any trust and whether an election out is warranted. Allocate the GST exemption explicitly for any generation-skipping transfers.
• Advise on remarriage implications and DSUE preservation strategies. If the surviving spouse is considering remarriage, advise on the last deceased spouse rule and the risk that the current DSUE will be replaced by the new spouse's (potentially smaller or zero) DSUE. Gifting strategies to use the current DSUE before remarriage should be evaluated with estate planning counsel.
• Confirm step-up in basis analysis for appreciated assets. Identify assets with significant unrealized gain included in the gross estate. Confirm the step-up in basis result under IRC 1014. If the estate is in a community property state, confirm the IRC 1014(b)(6) full community property step-up applies to both halves.
• File Form 706 and retain proof of filing. For Rev. Proc. 2022-32 filings, retain evidence of timely filing (certified mail receipt, IRS acceptance confirmation) as proof the return was filed before the applicable five-year deadline.

Frequently Asked Questions

Related Practitioner Guides

The following guide covers a filing obligation that arises alongside the Form 706 estate tax return during estate administration.

• IRC 24 Child Tax Credit OBBBA Guide -- estate planning clients with minor children who are the Form 706 filers are typically above the IRC 24 CTC phase-out threshold; understanding the CTC interaction is part of comprehensive wealth transfer planning.
• IRC 2503 Annual Gift Tax Exclusion and Crummey Trust Guide -- Form 706 filers need to understand the annual exclusion to properly report cumulative taxable gifts; the two guides are directly complementary.
• Form 1041 trust and estate income tax guide -- while Form 706 reports the estate tax on the gross estate, the estate also has a separate income tax obligation during administration: income earned by estate assets after the date of death is reported on Form 1041, which covers distributable net income (DNI), the distribution deduction, and beneficiary inclusion. Practitioners handling an estate should address both the Form 706 estate tax return and the Form 1041 fiduciary income tax return.
• Generation-skipping transfer tax IRC 2601-2642 inclusion ratio and GST exemption guide -- Form 706 Schedule R is where the GST exemption is allocated at death, making the GST tax the direct companion to the estate tax return; this guide covers the inclusion ratio, applicable fraction, the three types of generation-skipping transfers, the ETIP trap, and the Form 706-GS returns.
• IRC 2010 Permanent Estate and Gift Tax Exemption Guide -- the portability election (DSUE) is made on Form 706; the permanent $15M BEA is the foundational rule that the Form 706 portability election preserves.
• IRC 6166 Estate Tax Installment: Closely Held Business Election -- Installment payment election made on Form 706 for estate tax attributable to qualifying closely held business interests: the 35% test, 14-year schedule, and acceleration events.
• IRC 2053: Estate Deductions -- Form 706 Schedule J (funeral and administration expenses) and Schedule K (debts of the decedent and mortgages) are the two deduction schedules that translate the IRC 2053 statutory categories into the Form 706 reporting structure; practitioners completing Form 706 must know which expenses qualify under each IRC 2053 category and how the Reg. 20.2053-4(b) substantiation rules apply to contested or contingent claims at the time of filing.
• IRC 2035: Gifts Within 3 Years of Death -- Form 706 Schedule G reports property transferred within 3 years of death that is includible under IRC 2035(a) (transferred interests subject to 2036-2038 or 2042) plus the gift taxes paid within 3 years under IRC 2035(b); the Schedule G instructions are the operational translation of IRC 2035 into Form 706 line-level reporting, and practitioners completing the return must correctly classify which prior transfers belong on Schedule G.
• IRC 2056: Marital Deduction and QTIP Election -- Schedule M (Form 706) is where the executor makes the QTIP election under IRC 2056(b)(7); a timely-filed, complete Schedule M entry for each trust is the only way to perfect the QTIP election; a missed or incomplete election is irrevocable after the Form 706 due date; practitioners completing Form 706 should read IRC 2056 and this guide in conjunction with the Schedule M instructions at IRS.gov before filing.
• IRC 6035 and Form 8971 estate basis consistency reporting -- when a Form 706 is required, the executor must also file Form 8971 and furnish Schedule A to each beneficiary under IRC 6035; the estate-tax value finally determined on Form 706 caps the beneficiary's income tax basis under IRC 1014(f), and this guide covers the T.D. 9991 final regulations, the 30-day filing deadline, and the IRC 6724 reasonable cause defense.
• IRC 2040 jointly held property JTWROS gross estate inclusion -- Schedule E (Form 706) reports jointly held property, splitting qualified joint interests between spouses (the automatic 50% rule) from all other joint interests governed by the IRC 2040(a) full-inclusion contribution rule; practitioners completing Schedule E must document each survivor's contribution to determine the includible fraction and the corresponding IRC 1014(b)(9) basis step-up.