A bypass trust works by splitting a married couple’s estate in two when the first spouse dies: instead of leaving everything to the survivor, the deceased spouse’s share (up to the federal estate tax exemption, $15 million in 2026) drops into an irrevocable trust that pays income to the surviving spouse for life and then passes to the children. Because the survivor never owns those assets outright, they don’t get counted in the survivor’s estate at the second death. Both spouses’ exemptions get used, and a couple can shield up to $30 million from the 40% federal estate tax.1Internal Revenue Service. What’s New – Estate and Gift Tax
When the Trust Actually Comes Into Existence
You don’t fund a bypass trust during your lifetime. It sits dormant inside a broader estate plan, usually written into a revocable living trust or a will. While both spouses are alive, the bypass trust is just language on a page.
It comes to life at the first death. At that moment, the instructions kick in, the trust becomes irrevocable, and a portion of the deceased spouse’s assets gets retitled into it. The amount transferred is typically capped at the federal estate tax exemption in effect that year, which is $15 million for 2026 and indexed to inflation going forward.2Office of the Law Revision Counsel. 26 U.S. Code 2010 – Unified Credit Against Estate Tax That transfer is the pivot the whole strategy turns on. Once those assets sit inside the trust, they are legally separate from anything the surviving spouse personally owns.
The Three Roles
The grantor is the spouse who dies first. Their assets fund the trust.
The trustee manages the trust’s investments and decides on distributions. In many families, the surviving spouse serves as trustee, which gives them day-to-day control over the money as long as they follow the rules in the trust document. Larger or more complex trusts sometimes use a bank or professional trust company instead.
The beneficiaries come in two layers. The surviving spouse is the primary beneficiary during their lifetime. The remainder beneficiaries, usually the couple’s children, receive whatever is left after the survivor dies.
What the Surviving Spouse Can Take Out
Income and principal are treated very differently, and the difference is what makes the tax benefit hold together.
All the income the trust generates (interest, dividends, rental income) flows to the surviving spouse automatically. That gives them a reliable stream of money without touching the underlying assets.
Principal is another story. Distributions of principal are limited to an ascertainable standard called HEMS: health, education, maintenance, and support. The surviving spouse can pull principal for medical bills, tuition, mortgage payments, property taxes, and other costs tied to maintaining their standard of living. They cannot withdraw principal for any reason they choose, and they cannot give it away.
The HEMS limitation comes straight from the tax code. A power over trust assets that is confined to health, education, support, or maintenance is specifically excluded from being treated as a “general power of appointment.”3Office of the Law Revision Counsel. 26 U.S. Code 2041 – Powers of Appointment If the surviving spouse had unrestricted access instead, the whole trust would get pulled back into their taxable estate and the strategy would collapse.
What Happens at the Second Death
When the surviving spouse dies, whatever remains in the trust passes directly to the remainder beneficiaries. Since the surviving spouse never owned those assets, they are not part of the survivor’s estate for tax purposes. That is the “bypass.”
The first spouse’s exemption sheltered the assets when the trust was funded. The surviving spouse’s own exemption still covers their separate estate. Both exemptions get used, which is the point.
Appreciation stays outside the second estate too. If the trust is funded with $10 million at the first death and grows to $18 million by the time the survivor dies, the full $18 million passes to the children without estate tax. For families expecting significant growth in their investments or business interests, that sheltered appreciation is often worth more than the original exemption amount.
The Simpler Alternative: Portability
Since 2011, couples have had another way to use both exemptions without setting up a trust. It’s called portability. When the first spouse dies, the executor files a federal estate tax return (Form 706) and elects to transfer the deceased spouse’s unused exemption to the survivor. The transferred amount is known as the Deceased Spousal Unused Exclusion, or DSUE. In 2026, a spouse who dies with a $5 million taxable estate can pass the remaining $10 million of unused exemption to the survivor, giving that survivor a personal exemption of $25 million.4Internal Revenue Service. Instructions for Form 706
Portability is simpler than running a trust for decades. No trustee, no retitling, no separate tax returns. And because the assets stay in the surviving spouse’s estate, they receive a second step-up in tax basis at the second death, which can eliminate large capital gains for the heirs.
Portability is not automatic. The executor has to file Form 706 within nine months of death, with a six-month extension available; a late-filing window runs up to five years from the date of death.4Internal Revenue Service. Instructions for Form 706 Estates that don’t otherwise owe estate tax still have to file the full return just to preserve the exemption. Skip the filing and the exemption is gone for good.
When the Trust Still Beats Portability
Portability didn’t retire the bypass trust. Several situations still favor the trust:
- Future appreciation. Portability transfers a fixed dollar amount. A bypass trust removes the assets themselves along with everything they earn afterward.
- Generation-skipping transfer tax. The GST exemption is not portable between spouses. If you want to leave assets to grandchildren without triggering the GST tax, a bypass trust funded at the first death is the only way to use both spouses’ GST exemptions.5Library of Congress. The Federal Estate, Gift, and Generation-Skipping Transfer Taxes
- Insurance against law changes. Once the trust is funded, the sheltered amount is locked in. Portability depends on whatever the tax law says decades from now.
- Asset protection. An irrevocable trust generally keeps its assets away from the surviving spouse’s creditors, lawsuits, divorcing new spouse, and later remarriage. Assets held outright have none of that.
The direction the remainder passes is also fixed. If the surviving spouse remarries and later dies, the trust goes to the original beneficiaries the couple named, not to the new spouse. For blended families, that alone is often reason enough.
The Basis Step-Up Trade-Off
The biggest hidden cost of a bypass trust is on the capital gains side. Under federal law, inherited property gets a new tax basis equal to its fair market value on the date of death.6Office of the Law Revision Counsel. 26 U.S. Code 1014 – Basis of Property Acquired From a Decedent That step-up wipes out the unrealized gains that built up during the owner’s life.
Trust assets get a step-up at the first death, when the trust is funded. They do not get a second step-up at the surviving spouse’s death, because the survivor never owned them. Say the trust holds stock bought for $500,000 and worth $2 million when the first spouse dies. Basis steps up to $2 million. If the stock grows to $4 million by the time the survivor dies fifteen years later, the children inherit with a $2 million built-in gain and owe capital gains tax when they sell.
Under a portability strategy, those same assets would have stayed in the surviving spouse’s personal estate and received a full step-up to $4 million at the second death. The heirs would owe no capital gains at all. For couples whose combined estate is well under $30 million and unlikely to face estate tax either way, a bypass trust can produce a net tax increase rather than a saving. Running the numbers with a tax advisor before locking in the structure is the whole ballgame.
Compressed Trust Income Tax Brackets
Trust income is taxed on its own compressed schedule. For 2026, a trust hits the top federal income tax rate of 37% once its retained income clears roughly $16,000. An individual doesn’t reach that same 37% rate until income exceeds about $626,000.
Any income the trust earns and holds back gets taxed at the top rate almost immediately. The usual workaround is to distribute income to the surviving spouse, who will typically be in a lower personal bracket. HEMS restrictions and the trust document’s language can limit how flexibly that gets done, so drafting matters. A rigid trust can end up handing the IRS thousands of dollars a year that a well-drafted one would have kept in the family.
What It Costs to Run
A bypass trust needs administration for as long as the surviving spouse lives, which could be twenty or thirty years. If a bank or trust company serves as trustee, annual fees typically run around 1% of trust assets: a $5 million trust would pay roughly $50,000 a year. A family-member trustee cuts that cost, but the trust still needs its own federal income tax return (Form 1041) each year, and professional preparation runs several hundred dollars annually.
The trust also needs its own taxpayer identification number, its own bank and brokerage accounts, and clean records. Commingling trust money with the surviving spouse’s personal accounts can unwind the tax benefits and pierce the asset protection. Those ongoing costs belong in the calculation alongside the projected tax savings, because for many couples they’ll add up to real money over the life of the trust.