You may already have a will, revocable trust, and neatly organized investment accounts. That doesn't mean your estate plan will preserve both spouses' tax exemptions or protect your family from New York estate tax. For a Queens couple with real estate, brokerage assets, and a closely held business, the difference between a plan that looks complete and one that works often appears only after the first death.
The question “what is a credit shelter trust?” is therefore practical, not academic. A credit shelter trust can lock assets and future appreciation outside the surviving spouse's taxable estate, but it also creates restrictions, administration, and a possible basis tradeoff. In 2026, I wouldn't recommend one just because an old estate-planning template includes an AB trust. I'd recommend it when a specific tax or family objective justifies the machinery.
The Couple Who Almost Lost Half Their Estate
A Queens couple owned rental properties, a valuable home, and a taxable brokerage account. Their wills left everything to each other, which seemed practical. The surviving spouse would need the assets, and the unlimited marital deduction generally permits property to pass between spouses without federal estate tax at the first death. Their attorney mentioned portability, but no one treated the federal estate-tax return as a post-death deadline requiring immediate attention.
The first spouse died. The survivor received the assets outright and continued managing the portfolio. Years later, a review exposed two gaps: the executor had not filed the federal estate-tax return to elect portability, and no separate trust had preserved the first spouse's exemption. The property and investments had also appreciated, increasing the amount exposed at the survivor's death.
At the federal level, filing Form 706 could have preserved the deceased spouse's unused exemption through portability. A credit shelter trust takes a different approach. Assets up to the first spouse's applicable exclusion are transferred to an irrevocable trust, while the balance may pass under the marital deduction. That structure can preserve tax protection and keep future appreciation outside the survivor's taxable estate, but it gives up some flexibility and may affect basis planning.
New York changes the analysis. Federal portability does not transfer a deceased spouse's unused New York exemption. A couple that solves only the federal issue can still leave a state estate-tax exposure at the second death, even if federal estate tax is not the primary concern. For New York clients, that state-specific risk can justify trust planning when federal portability makes a bypass trust look unnecessary.
Practical rule: Any plan relying on an election, funding formula, or post-death deadline must identify the person responsible for completing it.
Every couple does not need a bypass trust. The right choice depends on asset ownership, projected growth, residence, family structure, desired access, and tolerance for administration. A trust may lock in tax protection, while outright ownership or portability can preserve simplicity and a possible basis step-up. Review those trade-offs before accepting an outdated AB-trust formula. Inertia is not a strategy.
How a Credit Shelter Trust Works
A credit shelter trust, also called a bypass trust or AB trust, is an irrevocable trust funded when the first spouse dies. It uses that spouse's federal estate-tax exclusion without placing the trust assets in the surviving spouse's taxable estate.
The trust holds those assets under defined terms. The surviving spouse may receive income and, if the document allows it, principal for stated needs. The assets and their future appreciation generally remain outside the survivor's estate. The Cornell Wex overview of credit shelter trusts describes the structure and its relationship to the marital deduction.
The funding sequence
The mechanics usually follow three stages:
The first spouse dies. The estate is valued, and the funding formula identifies the amount intended for the credit shelter trust.
The trust receives the sheltered amount. Assets covered by the applicable exclusion move into the irrevocable trust. The balance may pass outright to the surviving spouse or into a marital trust, depending on the estate plan.
The survivor receives controlled access. The trust can provide financial support while directing the remaining assets to children or other beneficiaries after the survivor's death.
The key distinction is ownership. Assets placed in the trust are generally excluded from the survivor's taxable estate. Assets passing outright to the survivor become part of that estate. Appreciation on trust assets generally remains outside the survivor's estate as well.
Where the assets go
| Asset | Destination | Reason |
|---|---|---|
| Amount covered by the first spouse's applicable exclusion | Credit shelter trust | Uses the first spouse's exclusion and keeps future growth outside the survivor's estate |
| Remaining assets intended for the survivor | Survivor directly or marital trust | May qualify for the unlimited marital deduction |
| Assets intended for children or other beneficiaries | As directed by the estate plan | Preserves control over ultimate beneficiaries |
A credit shelter trust does not leave the survivor without support. A well-drafted document can provide income and access to principal under stated standards. The trade-off is direct: the survivor gives up unrestricted ownership in exchange for tax protection and control over the remainder beneficiaries.
The structure made more sense when the federal exemption was much lower. Today, the decision is a trade-off between locking in tax protection and preserving flexibility, a possible basis step-up, and simpler administration. New York clients also need separate state-tax analysis, because federal portability does not solve every New York estate-tax concern.
Why the Federal Tax Case Has Weakened
Credit shelter trusts became common because the federal exemption was once small enough that married couples often needed both spouses' exclusions. The exemption was $600,000 for many years before 1997, rose to $1 million in 2002 and 2003, reached $3.5 million in 2009, and increased to $5 million in 2010 and 2011, as summarized in the Hofstra Law scholarship discussing credit shelter trusts and exemption history.
That history explains the older planning instinct. If the first spouse left everything outright to the survivor, the first spouse's exemption could go unused. The survivor then owned both estates, and the family faced a larger taxable estate at the second death. A bypass trust solved that problem by using the first exclusion immediately.
Portability changed the default
Federal portability rules arrived in 2010 and applied to deaths in 2011. A surviving spouse can generally claim the deceased spouse's unused federal exemption by filing an estate-tax return and making the election. The Commerce Trust comparison of credit shelter trusts and portability explains why portability reduced the need to divide assets between spouses solely to preserve federal exemptions.
The current federal amounts are dramatically higher than the historical levels. The exclusion is $13.99 million per person for 2025, and sources cited for 2026 place it at about $15 million per person, or roughly $30 million for a married couple using portability. The 2025 figures and the scheduled change in the exclusion are discussed in this Wells Fargo Advisors credit shelter trust overview.
That doesn't make the trust obsolete. It changes the question. A couple with a straightforward family structure and assets comfortably below the federal threshold may value flexibility and simplicity more than locking in the first spouse's exclusion. A couple expecting major appreciation, managing a blended family, or living in a state without portability may reach the opposite conclusion.
The federal exemption is also scheduled to change after 2025 absent legislative action. That means a trust drafted for today's threshold can become poorly matched to the family's balance sheet later. Review matters more than labels.
Credit Shelter Trust vs QTIP Trust vs Portability
These three tools address different problems. Treating them as interchangeable produces mediocre planning.
A credit shelter trust uses the first spouse's exclusion at death. The assets remain in an irrevocable trust, and appreciation can stay outside the survivor's taxable estate. The survivor receives whatever access the document allows, while the trust preserves control over the eventual beneficiaries.
A QTIP trust takes a different route. It qualifies for the marital deduction, supports the surviving spouse, and reserves the remainder for beneficiaries selected by the first spouse. That makes it especially useful in a second marriage where one spouse wants to provide for the survivor without giving the survivor unrestricted authority over assets that should ultimately pass to children from a prior relationship.
Portability is the simplest federal option. It doesn't require a separate bypass trust. The executor files Form 706 and elects the deceased spouse's unused federal exclusion for the survivor. The survivor then retains broader ownership flexibility, but portability doesn't provide the same control, creditor protection, or state-tax solution as a properly designed trust.
Which tool wins
| Planning concern | Credit shelter trust | QTIP trust | Portability |
|---|---|---|---|
| Preserve federal exclusion | Uses it at the first death | May defer tax through the marital deduction | Transfers unused federal exclusion by election |
| Protect future appreciation | Strong, because trust assets stay outside the survivor's estate | Depends on inclusion and drafting | Weaker, because assets generally remain owned by the survivor |
| Protect children from a prior relationship | Strong control | Particularly strong remainder control | Limited, unless paired with other planning |
| Keep administration simple | No | No | Generally yes |
| Address New York estate tax | Can help, subject to state-specific drafting | Requires separate analysis | Doesn't transfer New York exemption |
My recommendation is direct. Use portability as the federal default for a simple married couple when flexibility matters and state estate tax isn't driving the plan. Use a QTIP structure when the first spouse needs to control the remainder while supporting the survivor. Use a credit shelter trust when appreciation, asset protection, generation-skipping objectives, remarriage concerns, or state estate tax justify the restrictions.
Portability is not a substitute for reviewing beneficiary designations, titling, and family objectives. It is an election, not a complete estate plan.
The New York Twist Most Articles Skip
New York changes the answer because federal portability doesn't carry over to the state estate tax system. A surviving spouse may preserve the deceased spouse's unused federal exclusion, but that federal election doesn't create a portable New York exclusion.
That distinction matters to families with New York residences, rental properties, business interests, and concentrated investments. A couple can have little or no federal estate-tax exposure while still needing a state-level plan. A credit shelter trust can preserve assets outside the survivor's estate in a way that portability alone cannot.
The cliff makes modeling essential
New York's estate tax includes a cliff structure. An estate that exceeds the applicable state exclusion by more than the permitted margin can lose the exclusion and face tax calculated against the larger estate rather than only the excess. Because the exact threshold and rules can change, your attorney and CPA must model the current New York calculation rather than rely on a federal estimate.
Take a New York couple with $20 million in combined assets. That figure doesn't establish a tax bill by itself, and I wouldn't promise a savings amount without reviewing ownership, deductions, gifts, residency, insurance, and asset values. It does show why a federal-only analysis can be incomplete. If the first spouse leaves everything outright to the survivor, the survivor may hold the full portfolio at the second death. A properly funded bypass trust may keep part of the first estate, and its subsequent growth, outside that calculation.
New York planning point: Portability can preserve a federal benefit. It doesn't solve a New York estate-tax problem.
The trust also has to be funded correctly. A provision buried in a will doesn't protect an account that passes by beneficiary designation to the survivor. Real estate, brokerage accounts, partnership interests, and business interests each require an asset-specific review.
New York families should also resist a simplistic “trust equals tax savings” conclusion. Trust terms can affect basis planning, liquidity, investment control, and the survivor's access to capital. The right answer may combine a credit shelter trust, a marital trust, portability, life insurance planning, and carefully coordinated ownership.
Two Illustrative Examples
The same wealth level can produce two different recommendations. The following examples use $25 million only as a planning illustration, not as a prediction of tax owed. Actual results depend on the documents, asset ownership, deductions, prior gifts, residency, valuation, and applicable law.
Example one, portability fits
A married couple owns $25 million, primarily in marketable securities. They have a straightforward family structure, no New York estate-tax exposure, and no special asset-protection or remarriage concern. The first spouse dies, and the executor files Form 706 to elect portability.
The survivor retains direct ownership and investment flexibility. If the combined available federal exclusions cover the taxable estate at the survivor's death, the couple may achieve the intended federal result without placing assets in a bypass trust. The family avoids the added trustee administration and restrictions that come with an irrevocable trust.
That doesn't mean the couple should skip planning. The executor still needs to handle the election properly, and the family should review the portfolio, beneficiaries, and future growth. But on these facts, a credit shelter trust may be overkill.
Example two, the New York facts change the answer
Another couple also owns $25 million, but the assets include a New York brownstone, rental real estate, and a closely held business. The first spouse's plan funds a credit shelter trust with suitable assets, while the survivor receives support under the trust terms. The couple also evaluates portability for federal purposes.
Here, the trust can serve several jobs. It may preserve the first spouse's state-tax position, keep future appreciation outside the survivor's estate, protect the business interest from an unplanned change in family control, and preserve assets for intended beneficiaries. The trust isn't automatically correct, but the reasons for using it are much stronger.
| Factor | Example 1, National Couple | Example 2, New York Couple With Real Estate |
|---|---|---|
| Wealth used for illustration | $25 million | $25 million |
| Main assets | Marketable securities | Brownstone, rentals, closely held business |
| State issue | No New York exposure | New York estate-tax analysis required |
| Likely federal tool | Portability may be sufficient | Portability may be paired with a trust |
| Main tradeoff | Simplicity and flexibility | Control, state planning, and growth protection |
The point is not that every $25 million estate needs a trust. Asset type and jurisdiction can matter as much as net worth. A national portfolio and a New York real-estate family may need entirely different structures.
Pros, Cons, and Trustee Duties
A credit shelter trust earns its place by solving a defined problem. Its advantages are substantial when the facts support them:
- Locks in exemption use: The first spouse's exclusion is used rather than left dependent on a later election.
- Removes future appreciation: Growth on trust assets can remain outside the survivor's taxable estate.
- Protects family control: The trust can direct assets to children or other beneficiaries after the survivor's death.
- Adds a layer of protection: Properly drafted terms may provide friction against the survivor's creditors or a later remarriage.
- Supports broader planning: The structure can fit generation-skipping and state estate-tax objectives.
The costs are just as real. The trust is generally irrevocable after funding, so the survivor can't treat every asset as personal cash. Trust assets may not receive a basis adjustment at the second death in the same way assets included in the survivor's estate might. That basis tradeoff can outweigh estate-tax savings for families whose main concern is selling appreciated property.
Administration also continues after the first death. The trustee must maintain separate records, monitor investments, apply distribution standards, and coordinate tax reporting, including Form 1041 when required. The trustee must also keep the trust's situs, governing terms, and investment approach under review as family circumstances and exemption law change.
My candid view: If portability delivers the federal result and New York tax isn't driving the analysis, don't accept permanent restrictions merely because an old document uses an AB formula.
The opposite warning matters too. Skimping on administration after funding is a mistake. A trust that owns no properly transferred assets, lacks records, or misses required filings may fail to deliver the intended result.
A credit shelter trust is no longer a default for every married couple. It is a targeted tool. Use it when tax exposure, control, protection, or family dynamics pay for the complexity.
Action Steps and Advisor Checklist
Bring these questions to your estate attorney and CPA:
Read the funding formula. Does the will or revocable trust identify which assets fund the credit shelter trust, and does the formula respond to the current federal exclusion?
Confirm prior elections. If a spouse has already died, find out whether the executor filed Form 706 and elected portability. Do not assume the election happened because the estate paid no federal tax.
Run two calculations. Model the federal estate tax separately from the New York estate tax. Portability may address the first calculation while leaving the second untouched.
Review asset ownership. Match each property, brokerage account, partnership interest, business interest, insurance policy, and retirement account to its title and beneficiary designation.
Test liquidity. Determine whether the trust can hold assets that produce usable income and whether the survivor can access principal under the proposed standard.
Compare basis consequences. Ask whether keeping assets outside the survivor's estate could sacrifice a valuable basis adjustment at the second death.
Choose the default deliberately. For a simple family with no meaningful New York issue, portability may be the default. For a New York family with real estate, business growth, or blended-family concerns, a trust may be the exception worth making.
Schedule the next review. Revisit the plan when federal exemption law changes, when a property or business value shifts materially, or when the family structure changes.
For many high-net-worth couples in 2026, the question isn't “Do I have an AB trust?” It's “Which goal requires one, and which goals are better served by portability, basis planning, and simpler administration?” Get that answer in writing, then fund and administer the plan accordingly.
Blue Sage Tax & Accounting Inc. can model federal and New York estate-tax outcomes, review trust funding and portability issues, and prepare estate and trust tax returns. Visit Blue Sage Tax & Accounting Inc. to arrange a focused review of your current documents, assets, and next planning decisions.