Bitcoin & the Unlimited Marital Deduction: Estate Planning for Married Couples

Q: Can a non-citizen spouse use the unlimited marital deduction for Bitcoin?

No. The unlimited marital deduction is not available for transfers to non-citizen spouses. Instead, a Qualified Domestic Trust (QDOT) under §2056A must be used. The QDOT defers estate tax—estate tax is due as distributions are made from the trust (other than income) or when the surviving non-citizen spouse dies. Bitcoin held in a QDOT requires a US trustee and additional custody planning. An elevated annual gift tax exclusion ($185,000 in 2026, indexed) applies to lifetime gifts between spouses when one is a non-citizen.

Q: What is the bypass trust and when is it better than portability for Bitcoin?

A bypass trust (also called a credit shelter trust or B trust) uses the first-to-die spouse's estate tax exemption at the first death rather than relying on portability. Bitcoin placed in the bypass trust at the first death is not included in the surviving spouse's estate—so all future appreciation accrues outside the taxable estate. The bypass trust is superior to portability for Bitcoin because: (1) portability transfers a fixed dollar amount of exemption—it doesn't transfer the appreciation exemption; (2) Bitcoin in a bypass trust compounds free of estate tax; (3) the DSUEA is not inflation-indexed and not available if the surviving spouse remarries and that spouse also dies. For large, fast-appreciating Bitcoin positions, the bypass trust's appreciation advantage is substantial.

The unlimited marital deduction is one of the most powerful provisions in the estate tax code—and one of the most misunderstood. Married Bitcoin holders often assume that leaving everything to a spouse at death solves the estate tax problem. It does not. It defers it, often into a larger problem, at the second death.

For Bitcoin families where one or both spouses hold significant positions, the planning decisions made at the first death—whether to use the marital deduction fully, fund a bypass trust, elect portability, or structure a QTIP—will determine whether the next generation receives Bitcoin with an efficient tax basis or inherits a concentrated estate tax bill alongside their inheritance.

This guide covers the complete framework for married Bitcoin holders: how the marital deduction works, the deferral trap, the portability election, when the bypass trust outperforms portability for fast-appreciating Bitcoin, QTIP trust mechanics, the non-citizen spouse limitation, and the custody transition challenge that's unique to Bitcoin estates.

1. The Unlimited Marital Deduction: The Basics

Under IRC §2056, an unlimited amount of property may be transferred from one US citizen spouse to another US citizen spouse—whether by gift during life (§2523) or bequest at death (§2056)—with no transfer tax whatsoever. No estate tax. No gift tax. Unlimited. The full value of Bitcoin passing to a surviving US-citizen spouse at death is completely exempt from estate tax.

What "Unlimited" Actually Means

The deduction is genuinely unlimited. A Bitcoin holder with $50 million in BTC can leave all of it to a surviving US-citizen spouse with zero federal estate tax at the first death. No exemption required. No tax return in many cases (though a return may still be advisable to elect portability—more on this below).

The Trade-Off: Deferred, Not Eliminated

The unlimited marital deduction is a deferral mechanism—not an elimination mechanism. Bitcoin that passes to the surviving spouse is added to the surviving spouse's estate. When the surviving spouse dies, the combined estate is subject to estate tax on everything above the surviving spouse's available exemption. If Bitcoin has appreciated substantially between the two deaths, the second-death estate tax bill can be far larger than the first-death tax would have been.

⚠️ The Deferral Trap for Bitcoin Estates

Scenario: Both spouses hold significant Bitcoin. First spouse dies, leaves all Bitcoin to surviving spouse. No tax at first death. Bitcoin doubles in value over the next decade. Surviving spouse dies with 2× the Bitcoin and 1× their personal exemption—but the first spouse's exemption was never used and is now only available if portability was elected. The full appreciation from both deaths compresses into one estate. The unlimited marital deduction solved nothing—it just moved the problem.

2. The Portability Election: Carrying Forward the Unused Exemption

The portability election, enacted in 2010 and made permanent by ATRA 2012, allows a surviving spouse to inherit the deceased spouse's unused estate tax exemption—the Deceased Spouse's Unused Exclusion Amount (DSUEA).

How It Works

If the first-to-die spouse has a $15 million exemption (the approximate 2026 OBBBA threshold—confirm with your advisor as final legislation may vary) and their taxable estate is only $3 million, the unused $12 million passes to the surviving spouse via a portability election. The surviving spouse can then apply up to $27 million of total exemption ($15M own + $12M inherited DSUEA) against their estate.

Filing Requirement

Portability is not automatic. It requires a timely filed Form 706 (federal estate tax return) for the deceased spouse's estate—even if no estate tax is actually due. The return must be filed within nine months of death (or 15 months with extension). Missing this deadline forfeits the DSUEA permanently.

💡 File Anyway

Many married Bitcoin holders with estates below the current exemption skip Form 706, assuming it's not needed. For any married couple where Bitcoin is a significant asset, filing a protective portability election is worth the cost. Bitcoin appreciation is not predictable. The DSUEA that seems unnecessary today may be critically important at the second death if Bitcoin is at $500,000/coin. The cost of the estate tax return is trivial compared to the value of the preserved exemption.

Portability Limitations for Bitcoin

Fixed dollar amount: The DSUEA is a fixed dollar figure set at the first death. It does not grow with Bitcoin appreciation. If Bitcoin triples between the first and second deaths, the DSUEA is still the same nominal dollar amount.
Remarriage forfeiture: If the surviving spouse remarries and the new spouse predeceases them, the DSUEA from the first marriage is forfeited. Only the most recently deceased spouse's unused exemption is portable. This is a significant risk for younger surviving spouses.
No GST exemption portability: Portability applies only to the estate and gift tax exemption—not to the generation-skipping transfer (GST) tax exemption. Each spouse's GST exemption must be used or lost at their own death.

3. The Bypass Trust: The Superior Structure for Bitcoin

The bypass trust (also called a credit shelter trust, B trust, or exemption trust) is the alternative to relying on portability. At the first death, Bitcoin equal to the deceased spouse's available exemption is placed in a bypass trust rather than passing directly to the surviving spouse. The bypass trust is not included in the surviving spouse's estate.

Why the Bypass Trust Outperforms Portability for Bitcoin

The key advantage of the bypass trust over portability is appreciation shelter:

Feature	Portability	Bypass Trust
Exemption used at first death	No — preserved for later	Yes — applied immediately
Future Bitcoin appreciation sheltered?	No — DSUEA is fixed $	Yes — all appreciation stays outside estate
Inflation protection	No — DSUEA not indexed	Yes — trust assets grow untaxed
GST exemption	Not portable	Can be allocated at first death
Remarriage risk	DSUEA forfeited if surviving spouse remarries and new spouse predeceases	Trust assets unaffected by surviving spouse's remarriage
§1014 step-up at second death	Yes — QTIP assets in surviving spouse's estate get step-up	No step-up for bypass trust assets (got step-up at first death)
Surviving spouse's income access	Full, direct access to all assets	Income only (mandatory); discretionary principal distributions
Control over ultimate beneficiaries	Surviving spouse can redirect assets to anyone	First-to-die names remainder beneficiaries (protected)

For a Bitcoin position expected to appreciate significantly over the next decade, the bypass trust's appreciation shelter advantage is compelling. Every dollar of Bitcoin that grows inside the bypass trust compound free of estate tax—both the principal and all future gains escape the surviving spouse's taxable estate entirely.

💡 Bypass Trust Math Example

Husband dies in 2026 with 20 BTC valued at $15 million. Places all 20 BTC in a bypass trust (equal to his full exemption). Wife's estate doesn't include the bypass trust Bitcoin. Ten years later, those 20 BTC are worth $50 million. At wife's death: $0 estate tax on the $50 million bypass trust. With portability instead: wife's estate includes $50 million of Bitcoin, offset by $27 million of combined exemption. Tax on $23 million × 40% = $9.2 million. Bypass trust saved $9.2 million in this example purely from shelter of appreciation.

The Step-Up Trade-Off

The bypass trust's one disadvantage: Bitcoin placed in the bypass trust receives a §1014 step-up at the first death (when funded), but does not receive a second step-up at the surviving spouse's death because it is not in the surviving spouse's estate. If Bitcoin in the bypass trust has further appreciated by the second death, the beneficiaries inherit with a basis equal to the value at the first death—not the second death.

For Bitcoin that is expected to be held for decades, this matters. If children will hold Bitcoin in the bypass trust without selling, the lack of a second step-up is irrelevant. If they will sell within a few years of inheriting, the step-up trade-off reduces the bypass trust's advantage for highly appreciated positions.

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4. QTIP Trusts: Marital Deduction with Control

A Qualified Terminable Interest Property (QTIP) trust under §2056(b)(7) qualifies for the unlimited marital deduction—no estate tax at the first death—while allowing the first-to-die spouse to control where the Bitcoin ultimately passes after the surviving spouse's death.

QTIP Mechanics

All trust income must be distributed to the surviving spouse at least annually
Principal distributions to the surviving spouse are discretionary (and often limited)
The surviving spouse cannot redirect the remainder—the first-to-die's choice of remainder beneficiaries is fixed in the trust document
QTIP trust assets are included in the surviving spouse's taxable estate at death
Bitcoin in the QTIP trust receives a §1014 step-up at the surviving spouse's death

When QTIP Makes Sense for Bitcoin

The QTIP is the right tool when:

Second marriage: You want to ensure Bitcoin passes to your children (not a surviving spouse's new partner or their children from another relationship)
Blended family: Children from a prior marriage should be protected as ultimate beneficiaries
Estate tax planning with step-up priority: You want the second step-up at the surviving spouse's death (QTIP assets are in the surviving spouse's estate)
Large combined estate: When the combined Bitcoin estate requires marital deduction at first death to avoid immediate tax, but the first-to-die wants control over ultimate distribution

QTIP Election Mechanics

The QTIP election is made by the executor on Form 706 for the deceased spouse's estate. It can be made for all or any specific portion of trust assets, allowing flexible allocation between the marital (QTIP) portion and bypass portion. The executor can elect QTIP treatment only for the portion of assets needed to reduce estate tax to zero—preserving the balance as a bypass trust.

5. The A/B Trust and Disclaimer Trust Structures

The Classic A/B Trust

The traditional A/B trust (or marital/bypass trust) pre-divides the estate into two shares:

A Trust (Marital Trust): Bitcoin passing to the surviving spouse (qualifies for marital deduction)
B Trust (Bypass Trust): Bitcoin equal to the exemption amount sheltered from the surviving spouse's estate

Under pre-2010 law (before portability), the A/B trust was the standard approach for every married couple above the exemption. Portability has made the classic A/B trust less critical for moderate estates—but for large Bitcoin positions where appreciation shelter is valuable, the bypass trust component remains superior.

The Disclaimer Trust

A disclaimer trust combines flexibility with the option to use a bypass trust. At the first death, all Bitcoin passes to the surviving spouse outright (maximizing the marital deduction). Within nine months of death, the surviving spouse may execute a qualified disclaimer under §2518—refusing part or all of the inheritance, which then passes to a bypass trust named in the deceased spouse's will.

The disclaimer trust strategy allows the decision to be made after death, with full information about the estate's size, Bitcoin price, and tax law at the time. If the bypass trust advantage is obvious at the first death, the surviving spouse disclaims into it. If portability is sufficient, they keep the assets and elect portability instead.

💡 Disclaimer Strategy for Bitcoin

Given Bitcoin's price volatility, the disclaimer trust is an excellent planning vehicle. The decision of how much to disclaim can be made after seeing Bitcoin's price at the first death—when the estate value and tax consequences are concrete. The surviving spouse and advisors can model portability vs. bypass trust economics with actual numbers and make the optimal choice within the nine-month window.

6. Bitcoin Custody Transition at Death

Bitcoin's custody structure creates a unique challenge at the first spouse's death that does not exist with traditional financial assets. When a financial account holder dies, the surviving spouse contacts the custodian and establishes their access. When a Bitcoin holder dies—especially one holding Bitcoin in self-custody—the surviving spouse may have no ability to access the Bitcoin without the private key or seed phrase.

The Custody Transition Problem

If Bitcoin is held in a hardware wallet under the deceased spouse's control, the surviving spouse needs the seed phrase or PIN to access it
If multi-signature (multisig) custody is used, the surviving spouse must understand the signing requirements and have access to the correct number of keys
If Bitcoin is at an exchange (Coinbase, Kraken, etc.), the death of the account holder triggers a standard estate claims process—slower but manageable
If Bitcoin is held in an SDIRA or trust, the trustee or custodian handles the administrative transition

⚠️ The Bitcoin Widow/Widower Problem

The most common Bitcoin estate failure: a surviving spouse is left as the primary beneficiary of a large Bitcoin position with no ability to access the funds—because the deceased spouse never shared custody credentials and held Bitcoin in self-custody. Estate attorneys have no legal mechanism to "recover" a private key. The Bitcoin is economically inaccessible even though it passes legally. Every married Bitcoin holder must address this in their estate plan—not as an afterthought, but as a primary planning objective.

Custody Solutions for Married Bitcoin Holders

Multi-signature wallet with trustee access: A 2-of-3 or 3-of-5 multisig scheme where the spouse holds one key and a professional trustee holds backup keys. Death of one key-holder does not lock the estate.
Institutional custody with estate planning provisions: Custodians like Coinbase Custody, Unchained, or BitGo can accommodate beneficiary designations and estate access protocols.
Trust-held Bitcoin: Bitcoin held in a revocable living trust with a successor trustee eliminates the custody transfer problem—the trustee administers the Bitcoin without probate.
Sealed estate instructions: A sealed letter (not in the will) kept with the attorney or a separate secure location with the seed phrase or custody access instructions. This must be handled with extreme security—anyone with this document has access to the Bitcoin.

7. Non-Citizen Spouse: The QDOT Requirement

The unlimited marital deduction is not available for transfers to non-citizen spouses. Congress's concern: a non-citizen surviving spouse could return to their home country, taking the deferred estate tax liability beyond US jurisdiction permanently.

Instead, Bitcoin passing to a non-citizen spouse must be held in a Qualified Domestic Trust (QDOT) under §2056A to qualify for any marital deduction. Key QDOT requirements:

At least one trustee must be a US citizen or domestic corporation
The trustee must withhold estate tax on any principal distributions (other than hardship exceptions)
Estate tax is triggered when the surviving non-citizen spouse dies or the trust terminates
For trusts with assets over $2 million, a US bank or trust company must serve as trustee (or a bond must be posted)

Bitcoin held in a QDOT requires institutional custody or a domestic trust company as trustee—self-custody by a non-citizen surviving spouse is generally not compatible with QDOT requirements. See our detailed guide on Bitcoin estate planning for non-citizen spouses.

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8. GST Exemption and the Marital Deduction

A critical interaction: the unlimited marital deduction does not allocate the decedent's GST exemption. If the entire Bitcoin estate passes to a surviving spouse via the marital deduction, the deceased spouse's GST exemption is wasted unless proactively allocated.

GST Exemption Allocation Strategies

Bypass trust with GST allocation: Fund a bypass trust equal to the GST exemption and allocate the exemption to it. The trust can skip the surviving spouse's generation and pass to grandchildren free of both estate tax and GST tax.
Dynasty trust: Allocate GST exemption to a dynasty trust funded at the first death—the trust can hold Bitcoin for generations without estate or GST tax. This is the most powerful multigenerational structure available for Bitcoin families.
QTIP with GST election: A QTIP trust can have GST exemption allocated to it (the "reverse QTIP election"), protecting distributions from GST tax on distributions to skip persons. Complex, but valuable for large multi-generational Bitcoin positions.

9. Practical Action Plan for Married Bitcoin Holders

Determine your combined estate size and exemption position. Add up all Bitcoin (at current price), real estate, retirement accounts, business interests, and other assets for both spouses. Compare to the current estate tax exemption. If combined estate is below the exemption, portability may be sufficient. If above, a bypass trust or more aggressive strategy is warranted.
Decide: marital deduction + portability OR bypass trust. For fast-appreciating Bitcoin positions, model the bypass trust's appreciation shelter over your expected time horizon. The bypass trust's advantage grows with time and appreciation rate. Your estate planning attorney can model both scenarios with your actual numbers.
Consider a disclaimer trust structure. A disclaimer trust builds optionality into your estate plan. It allows the surviving spouse to make the portability vs. bypass trust decision after the first death with full information about estate values and tax law. For Bitcoin, where price volatility makes pre-death planning uncertain, this flexibility has real value.
Address custody transition explicitly. Every married Bitcoin holder must have a documented plan for how the surviving spouse accesses the Bitcoin. This includes self-custody credentials, exchange account access, trust company contacts, and multi-sig key management. This should be a specific section of your estate plan—not an afterthought.
File Form 706 at the first death—even if not required. If you elect portability, it requires a timely filed estate tax return. Do not skip this step to save on accounting fees. The DSUEA may be worth millions and the filing deadline is absolute.
Allocate GST exemption at the first death. If you are using a bypass trust, consider allocating the deceased spouse's GST exemption to it at the first death rather than letting it expire unused. This transforms the bypass trust into a dynasty-trust-equivalent for GST purposes.
Non-citizen spouse: structure a QDOT before you need it. If one spouse is not a US citizen, the QDOT must be set up and Bitcoin transferred into it (or the will must be drafted to direct transfer) before the first death. QDOT treatment cannot be established retroactively after death without specific corrective mechanisms.

Frequently Asked Questions

Does the unlimited marital deduction eliminate Bitcoin estate tax?

No. The unlimited marital deduction defers Bitcoin estate tax to the second death—it doesn't eliminate it. Bitcoin that passes to a surviving US-citizen spouse at the first death incurs no estate tax then. But the surviving spouse's estate now includes all that Bitcoin, and estate tax applies at the second death on everything above the surviving spouse's available exemption. For large Bitcoin positions, proper planning at the first death is essential to avoid compounding the second-death tax bill.

What is the portability election for Bitcoin estates?

Portability allows a surviving spouse to inherit the deceased spouse's unused estate tax exemption (the DSUEA). If the first-to-die has a $15 million exemption and a $3 million estate, the unused $12 million transfers to the surviving spouse via a portability election on Form 706 (filed within 9 months of death). The surviving spouse can then shield up to $27 million from estate tax. Critical limitation for Bitcoin: the DSUEA is a fixed dollar amount—it does not grow with Bitcoin appreciation between the two deaths.

What is a QTIP trust and why use one for Bitcoin?

A Qualified Terminable Interest Property (QTIP) trust qualifies for the unlimited marital deduction while allowing the first-to-die to control the ultimate destination of Bitcoin after the surviving spouse's death. All income goes to the surviving spouse; the first-to-die names the remainder beneficiaries (typically children). This is critical for second marriages and blended families where the first-to-die wants to ensure Bitcoin passes to their own children, not to a surviving spouse's future partner or other heirs. QTIP assets receive a §1014 step-up at the surviving spouse's death.

Can a non-citizen spouse use the unlimited marital deduction for Bitcoin?

No. The unlimited marital deduction is not available for non-citizen spouses. Bitcoin passing to a non-citizen surviving spouse must be held in a Qualified Domestic Trust (QDOT) under §2056A to qualify for any marital deduction. The QDOT defers estate tax, with US trustee oversight and withholding on principal distributions. An elevated annual gift tax exclusion ($185,000 in 2026, indexed) applies to lifetime Bitcoin gifts to a non-citizen spouse.

What is the bypass trust and when is it better than portability for Bitcoin?

A bypass trust uses the first-to-die's exemption at the first death to shelter Bitcoin from the surviving spouse's estate—including all future appreciation. Portability only transfers a fixed dollar amount; it doesn't shelter appreciation. For Bitcoin expected to appreciate significantly, the bypass trust's appreciation shelter advantage is substantial. Additional advantages: bypass trust assets are protected if the surviving spouse remarries, and GST exemption can be allocated at the first death. The trade-off: no second §1014 step-up at the surviving spouse's death for bypass trust Bitcoin.

Does Bitcoin in a marital trust receive a §1014 step-up at death?

It depends on the trust structure. Bitcoin in a QTIP trust that is included in the surviving spouse's taxable estate receives a §1014 step-up at the second death—all pre-death appreciation eliminated. Bitcoin in a bypass trust is not in the surviving spouse's estate and receives no step-up at the second death (it received a step-up at the first death when funded). The choice between QTIP and bypass trust involves weighing the appreciation-shelter benefit against the double step-up opportunity.

The Bottom Line: The Marital Deduction Is a Planning Starting Point, Not an Endpoint

The unlimited marital deduction provides a powerful and flexible foundation for married Bitcoin estate plans—but treating it as the plan itself is a mistake. Every dollar of Bitcoin that passes to a surviving spouse via the marital deduction and then appreciates dramatically simply raises the second-death tax bill, potentially with interest.

The complete strategy for a married Bitcoin family combines:

Bypass trust or disclaimer trust to shelter appreciation from the surviving spouse's estate
Portability election as a backstop even when not immediately needed
GST exemption allocation to enable multigenerational Bitcoin transfer
QTIP trust when control over ultimate beneficiaries is essential
Explicit custody transition plan so the surviving spouse can actually access the Bitcoin
QDOT planning for any non-citizen spouse in the family

The marital deduction is the least expensive tax benefit available in the Internal Revenue Code. Use it thoughtfully—not as a default that defers a problem you could have solved.

This article is for informational purposes only and does not constitute legal, tax, or financial advice. Estate tax law is complex and highly fact-specific. OBBBA exemption thresholds referenced are projections subject to final legislation—confirm current exemption amounts with your tax advisor. Always consult qualified estate planning attorneys and CPAs for your specific situation.