Most married couples assume that leaving everything to each other is enough of a plan. It’s not always. A bypass trust, sometimes called a credit shelter trust or AB trust, is a legal arrangement that helps married couples take full advantage of both spouses’ estate tax exemptions. And that distinction matters more than people realize.
Here’s how it works. When the first spouse dies, a portion of their estate flows into the trust rather than passing directly to the surviving spouse. That portion gets sheltered from estate taxes when the surviving spouse eventually passes as well. Without this kind of planning, you’re likely leaving one spouse’s federal estate tax exemption on the table entirely. The surviving spouse inherits everything outright, which sounds fine, but it means the whole combined estate gets taxed under just one exemption at death. A bypass trust closes that gap by locking in both.
Who Typically Needs One
Not every married couple needs this. A bypass trust is built for families with larger estates, particularly those where the combined value of assets could realistically exceed the federal estate tax exemption threshold. According to the IRS, the federal estate tax exemption sits at $13.61 million per individual for 2024. That sounds like a lot. But this exemption is scheduled to sunset at the end of 2025 under current law, and if that happens, the threshold could drop significantly, pulling many more families into taxable territory. An estate tax planning lawyer can tell you where your estate stands today and what the upcoming changes might mean for your family. You can review the current federal exemption levels directly through the IRS estate tax guidance. Couples who tend to benefit most from a bypass trust often share a few things in common:
- Combined assets that could approach or exceed the federal exemption
- Real estate, business interests, or investment portfolios with real appreciation potential
- A goal of passing wealth to children or grandchildren while still protecting the surviving spouse
- Concern about where federal or state estate tax laws are heading
How the Trust Works in Practice
When the first spouse dies, the assets get divided. One portion, typically up to the exemption amount, moves into the bypass trust. The surviving spouse can still benefit from those assets. They can receive income the trust generates, and in some cases, they can access the principal for specific needs like healthcare or education. But because those assets live inside the trust and aren’t directly owned by the surviving spouse, they don’t get counted as part of their taxable estate at death.
The remaining assets can pass outright to the surviving spouse using the unlimited marital deduction. No estate tax is owed on that transfer. The end result is that both spouses’ exemptions get used, and a much larger portion of the estate can reach your heirs without being taxed down to a fraction of its value.
A Few Important Considerations
Bypass trusts aren’t perfect. Assets placed inside one don’t receive a stepped-up cost basis when the surviving spouse dies, which can create capital gains tax exposure for beneficiaries who later sell those assets. You’re essentially trading one tax concern for another, and it’s worth sitting down with someone who can run the actual numbers for your situation.
State estate taxes add another layer of complexity worth knowing about. Some states impose their own estate tax with exemptions far lower than the federal threshold. Depending on where you live, a bypass trust might make sense even for estates well below the federal limit. Working with an estate tax planning lawyer who knows your state’s specific rules isn’t optional in those cases, it’s the whole point.
One more thing worth mentioning. The IRS now allows portability of the federal exemption between spouses, which gives some couples a simpler alternative to the bypass trust structure. Simpler doesn’t always mean better, though, especially when state taxes are involved or when the estate holds assets with significant growth potential down the road.
Getting the Right Plan in Place
A bypass trust can be a genuinely meaningful part of a broader estate plan for the right couple. It protects the surviving spouse, preserves wealth for the next generation, and makes sure both spouses’ tax exemptions actually get used rather than wasted. Estate Planning Pros works with families to build estate plans that reflect their real financial picture, not a generic template. If you’re wondering whether a bypass trust fits your situation, speaking with an estate planning attorney is the right place to start.