Estate tax portability under IRC §2010(c) is the mechanism allowing a surviving spouse to use the deceased spouse's Deceased Spousal Unused Exemption (DSUE) for their own gift and estate tax purposes. Enacted in 2010 (Tax Relief Act of 2010) and made permanent in 2012 (ATRA), portability effectively doubles a married couple's combined federal exemption when properly elected. Under OBBBA's permanent $15M per-spouse exemption (effective 2026), portability enables a married couple to shield up to $30,000,000 from federal estate and gift tax (subject to inflation-indexing from 2027). The election is made on the deceased spouse's Form 706 - even if no estate tax is otherwise owed, the estate must file Form 706 within 9 months of death (extendable to 15 months) to preserve DSUE. Rev. Proc. 2022-32 provides automatic 5-year late election relief for estates not otherwise required to file Form 706. The "Last Deceased Spouse" rule under §2010(c)(4)(B)(i) restricts surviving spouses with multiple deceased spouses to using only the most recently deceased spouse's DSUE. The GST exemption is NOT portable - must be allocated through the estate or by survivor's affirmative allocation. OBBBA preserved portability mechanics without change.
DSUE = Lesser of (basic exclusion amount in year of death) OR (decedent's basic exclusion amount LESS taxable estate LESS adjusted taxable gifts during life)
Capped at: Decedent's basic exclusion amount in year of death (cannot exceed).
Available to: Surviving spouse for lifetime gifts and estate.
Required: Estate of deceased spouse files Form 706 with portability election (timely or under Rev. Proc. 2022-32 late relief).
| Step | Computation |
|---|---|
| Step 1 - Decedent's BEA | Basic Exclusion Amount in year of decedent's death ($15M in 2026, inflation-indexed thereafter) |
| Step 2 - Subtract decedent's taxable estate | Estate value AFTER deductions (marital, charitable, debts, expenses, etc.) |
| Step 3 - Subtract decedent's adjusted taxable gifts | Sum of lifetime gifts above annual exclusions, valued at time of gift |
| Result = DSUE | Amount transferred to surviving spouse |
| DSUE cap | Cannot exceed decedent's BEA in year of death |
Facts: Husband dies March 2026 with $3,000,000 taxable estate. H made $2,000,000 of taxable lifetime gifts. Wife is sole beneficiary. H's BEA in 2026 = $15,000,000.
Step 1: Decedent's BEA = $15,000,000
Step 2: Minus taxable estate = $15,000,000 - $3,000,000 = $12,000,000
Step 3: Minus adjusted taxable gifts = $12,000,000 - $2,000,000 = $10,000,000
DSUE = $10,000,000 available to surviving wife.
Wife's effective exemption: Her own $15M + H's $10M DSUE = $25,000,000 available for her lifetime gifts and ultimate estate (subject to her own subsequent gift use and inflation indexing of her own BEA).
If no portability election made: Wife stuck with only her own $15M exemption. The $10M DSUE is lost forever - cannot be recaptured.
| Filing Requirement | Detail |
|---|---|
| Form 706 (Estate Tax Return) | Required to elect portability - even if no estate tax due and even if estate is below filing threshold |
| Standard deadline | 9 months after date of death (§6075(a)) |
| Automatic 6-month extension | Form 4768 - extends to 15 months after death |
| Election mechanics | Filing Form 706 with all required information constitutes affirmative portability election unless box explicitly checked to opt out (§20.2010-2(a)(1)) |
| Opt-out election | Affirmative opt-out box on Form 706 - irrevocable; rare to elect out |
| Estate value information required | "Reasonable" valuation of gross estate; full appraisals not required for non-taxable estates per §20.2010-2(a)(7)(ii) |
| Closing letter or Account Transcript | IRS issues closing letter (or transcript) within ~12-18 months confirming DSUE amount |
For estates that did NOT file Form 706 timely (because no estate tax was otherwise owed), Rev. Proc. 2022-32 provides automatic relief allowing late portability election within 5 years of death.
| Rev. Proc. 2022-32 Requirements | Detail |
|---|---|
| Decedent died after December 31, 2010 (when portability first available) | Eligible if portability was available at death |
| Surviving spouse | Must be living US citizen or resident |
| Filing window | Form 706 filed within 5 years of decedent's date of death |
| Decedent's estate not otherwise required to file | Estate must have been below filing threshold (basic exclusion amount in year of death) |
| Form 706 marking | Top of Form 706 marked: "FILED PURSUANT TO REV. PROC. 2022-32 TO ELECT PORTABILITY UNDER §2010(c)(5)(A)" |
| No private letter ruling required | Self-executing relief; no PLR filing or fee needed (replaces prior PLR-based process) |
| Failure to qualify within 5 years | Must request PLR for §301.9100-3 relief - separate procedure with $13,200 user fee (2026, inflation-adjusted) |
If a surviving spouse has had multiple deceased spouses, only the DSUE from the MOST RECENT deceased spouse is available. Earlier-deceased spouses' unused DSUE is lost upon a subsequent spouse's death.
| Scenario | Available DSUE |
|---|---|
| Spouse A dies 2020 with $5M DSUE; surviving spouse remarries Spouse B; Spouse B dies 2025 with $8M DSUE; surviving spouse now dies in 2026 | DSUE = $8M (Spouse B - most recent). Spouse A's $5M is lost. |
| Spouse A dies 2020 with $5M DSUE; surviving spouse never remarries; surviving spouse dies 2026 | DSUE = $5M from Spouse A (only deceased spouse) |
| Spouse A dies 2020 with $5M DSUE; surviving spouse remarries Spouse B but never uses A's DSUE; Spouse B is still alive when surviving spouse dies in 2026 | DSUE = $5M from Spouse A (still "last deceased") |
| Strategy: Use earlier spouse's DSUE before remarrying or before new spouse dies | Surviving spouse can make a large lifetime gift using Spouse A's DSUE before Spouse B's death locks it out |
If surviving spouse with DSUE from earlier-deceased spouse plans to remarry, making a large lifetime gift that uses up the earlier DSUE before the new spouse predeceases protects the benefit. Once the new spouse dies, the earlier DSUE is permanently lost. Gift the earlier DSUE first, then the new spouse can supply fresh DSUE if they later predecease.
Per §2010(c)(2), the DSUE is applied BEFORE the surviving spouse's own basic exclusion amount when computing gift or estate tax. This is automatic - the surviving spouse doesn't choose the order.
| Order of Application | Effect |
|---|---|
| 1. DSUE from last deceased spouse | Used first against surviving spouse's taxable transfers |
| 2. Surviving spouse's own BEA | Used next, after DSUE exhausted |
| Practical implication | Surviving spouse can "use up" DSUE through lifetime gifts before remarrying, protecting against last-deceased-spouse rule |
| Pre-deceased spouse change | If surviving spouse remarries and new spouse dies, DSUE from earlier spouse is replaced by new spouse's DSUE; gifts already made under earlier DSUE remain valid (no recapture) |
| Exemption Type | Portability |
|---|---|
| Basic exclusion / unified estate & gift exemption | PORTABLE via §2010(c) DSUE election |
| GST exemption (§2631) | NOT PORTABLE - must be allocated by deceased spouse during life or by estate |
| Marital deduction (§2056) | Not a portability issue - unlimited deduction for transfers to citizen spouse |
| Annual gift exclusion (§2503(b)) | Not portable in the DSUE sense - each spouse has their own $19,000 per donee per year |
| Non-citizen spouse annual exclusion (§2523(i)) | Not portable; per-spouse only ($190,000 for 2026) |
| GST Allocation Mechanism | Detail |
|---|---|
| Automatic allocation under §2632(b)/(c) | Certain transfers automatically receive GST exemption allocation unless opt-out |
| Affirmative allocation on Form 706 Schedule R | Executor can allocate GST exemption to specific transfers at death |
| Late allocation - §2642(b)(3) / Reg §26.2632-1 | Limited late allocation relief available for missed timely allocations |
| Form 709 lifetime GST allocation | Annual allocation of GST exemption to lifetime gifts |
| Strategic allocation | Allocate to assets expected to appreciate; use of valuation discounts; allocation to GST trusts |
Per §2010(c)(5)(B), the IRS may examine the predeceased spouse's estate tax return to determine DSUE amount even AFTER the normal statute of limitations on assessment has run. This is a one-way street - IRS can look back to recompute DSUE if surviving spouse uses it, even decades later.
| SOL Aspect | Detail |
|---|---|
| Normal SOL on Form 706 | 3 years from filing under §6501(a) |
| DSUE redetermination authority | IRS can recompute DSUE upon use by surviving spouse - no SOL bar under §2010(c)(5)(B) |
| Practical implication | Maintain complete records of decedent's Form 706 and supporting valuations indefinitely for surviving spouse |
| Surviving spouse audit risk | When surviving spouse uses DSUE on gift or estate return, IRS may recompute DSUE through full review of decedent's estate |
| QDOT Scenario | DSUE Treatment |
|---|---|
| Citizen spouse dies; non-citizen surviving spouse | Marital deduction NOT automatic for non-citizen spouse; must use Qualified Domestic Trust (QDOT) under §2056A |
| DSUE with QDOT | DSUE is preliminary - amount not finalized until QDOT principal distributions are taxed or trust terminates |
| QDOT distribution event | Deferred estate tax on principal distributions; DSUE may be adjusted downward |
| Surviving spouse later becomes US citizen | QDOT no longer required; DSUE becomes available without QDOT constraints |
| Form 706 filing requirement | Required to elect portability even with QDOT |
Pre-portability planning often used "credit shelter trusts" (bypass trusts) to absorb the first spouse's exemption. Now, with portability, simpler "I love you" wills with outright spousal bequests may suffice federally. But state-level estate tax and GST exemption preservation still favor bypass trust structures in many cases.
| Plan Type | Federal Benefit | State Benefit | GST Benefit |
|---|---|---|---|
| Outright bequest to surviving spouse + portability | Achieves $30M federal exemption | Loses state exemption of first-to-die in states without portability (most state estate tax states) | Loses GST exemption of first-to-die |
| Bypass / Credit Shelter Trust | Preserves first-to-die's federal exemption in trust; ALSO preserves portability for unused amount | Preserves first-to-die's state exemption | Preserves first-to-die's GST exemption (with trust allocation) |
| QTIP trust | Achieves marital deduction + preserves option to elect portability AND/OR reverse QTIP for GST | Varies by state | Reverse QTIP election under §2652(a)(3) preserves GST |
Surviving spouses often assume Form 706 is only required for taxable estates. For estates below the filing threshold, Form 706 must STILL be filed to elect portability. Missing this filing costs DSUE permanently (unless late-relief under Rev. Proc. 2022-32 is available within 5 years).
For deaths in the past 5 years where portability was not timely elected, Rev. Proc. 2022-32 still permits late election. Practitioners reviewing estate plans should evaluate every recent deceased-spouse case for late portability eligibility.
The most common high-net-worth estate planning error. GST exemption is NOT portable. Wealthy clients planning for grandchildren or generation-skipping must allocate first-to-die's GST exemption to bypass trusts or risk losing $15M of GST shelter.
Widowed clients with sizeable DSUE who remarry risk losing the DSUE upon new spouse's death. Counsel widowed clients with DSUE to consider using it via lifetime gifts BEFORE remarriage if remarriage is anticipated.
State estate tax remains an issue in 12 states + DC. Most state estate taxes do NOT have portability. Bypass trust structures may still be essential for state-level exemption preservation even when federal portability eliminates federal estate tax.
For non-taxable estates filing Form 706 solely for portability, "reasonable" valuation is acceptable under §20.2010-2(a)(7)(ii). But the surviving spouse will need this valuation later when using DSUE. Inadequate documentation invites IRS recomputation under §2010(c)(5)(B) without SOL protection.
Late filings under Rev. Proc. 2022-32 MUST be marked: "FILED PURSUANT TO REV. PROC. 2022-32 TO ELECT PORTABILITY UNDER §2010(c)(5)(A)" at the top. Missing this notation can cause IRS to reject the late election.
Marital deduction (§2056) defers estate tax on transfers to citizen spouse. DSUE under §2010(c) transfers the deceased spouse's unused exemption to the survivor. These are DIFFERENT mechanisms - both available, both serve different purposes.
When surviving spouse uses DSUE on lifetime gifts or estate return, the executor's claimed DSUE may be challenged. Maintain decedent's full estate file (Form 706, valuations, gift history, supporting docs) for the surviving spouse's lifetime - the SOL on DSUE redetermination is open-ended.
Affirmative opt-out of portability is rare but irrevocable. Practitioners should verify that the opt-out box is NOT checked on Form 706 unless explicitly intended - some preparers default the opt-out without client direction.
Primary authority: IRC §2010 (unified credit against estate tax). §2010(a) (applicable credit amount). §2010(c) (applicable exclusion amount including DSUE). §2010(c)(2) (DSUE applies before surviving spouse's own basic exclusion). §2010(c)(3) (basic exclusion amount - $15M effective 2026 per OBBBA). §2010(c)(4) (DSUE definition). §2010(c)(4)(B)(i) ("last deceased spouse" rule). §2010(c)(5)(A) (portability election requirement). §2010(c)(5)(B) (IRS authority to redetermine DSUE without statute of limitations bar). §2056 (marital deduction - unlimited for transfers to US citizen spouse). §2056A (Qualified Domestic Trust for non-citizen spouse). §2502 (gift tax imposition). §2503(b) (annual gift exclusion - $19,000 per donee for 2026). §2523(i) (non-citizen spouse annual exclusion - $190,000 for 2026). §2601 (GST tax imposition - 40% rate). §2631 (GST exemption - $15M aligned with unified exemption; NOT portable). §2632 (allocation of GST exemption; automatic allocation rules). §2632(b) (automatic allocation to direct skips). §2632(c) (automatic allocation to indirect skips). §2642(b)(3) (late GST allocation relief). §2652(a)(3) (reverse QTIP election for GST). §6075(a) (Form 706 filing deadline - 9 months from death). §6081 (extension - 6 additional months via Form 4768). §6501(a) (general 3-year statute of limitations). §301.9100-3 (regulatory relief for late elections; user fee required). Treasury Regulations §20.2010-1 (DSUE general). §20.2010-2 (portability election on Form 706). §20.2010-2(a)(1) (election by filing). §20.2010-2(a)(7)(ii) (reasonable valuation for non-taxable estates - special asset valuation rule). §20.2010-3 (surviving spouse use of DSUE). §26.2632-1 (GST exemption allocation rules). Revenue Procedure 2022-32 (5-year late portability election relief; replaces 2-year Rev. Proc. 2017-34 relief; supersedes prior PLR-only relief; effective July 8, 2022). Revenue Procedure 2017-34 (prior 2-year late portability relief - replaced). Rev. Proc. 2014-18 (prior portability late election relief - replaced). Form 706 (United States Estate (and Generation-Skipping Transfer) Tax Return). Form 706 Schedule R (GST allocation). Form 4768 (extension of time to file Form 706). Form 709 (United States Gift (and Generation-Skipping Transfer) Tax Return). One Big Beautiful Bill Act, P.L. 119-21, §70106 (preserved portability mechanics unchanged; raised BEA to $15M effective 2026).