What Is a Bypass Trust?

A Bypass Trust is a type of irrevocable trust used in estate planning to minimize estate taxes and preserve wealth for future generations. It is often established by married couples as part of a two-part estate plan that takes advantage of both spouses' federal estate tax exemptions. This trust is sometimes referred to as a Credit Shelter Trust, Family Trust, or B Trust.

Purpose and Basic Structure

The core function of a Bypass Trust is to prevent the federal estate tax exemption of the first spouse to die from being wasted. When a person dies, they are allowed to pass a certain amount of assets — known as the estate tax exemption — free of federal estate tax. If all the deceased spouse’s assets are transferred directly to the surviving spouse, the deceased’s exemption might go unused, especially in earlier years when portability wasn’t allowed. A Bypass Trust resolves this by capturing the deceased spouse’s exemption amount in a trust, ensuring that those assets are excluded from the taxable estate of the surviving spouse.

Typically, a couple's estate plan includes two trusts: the Marital Trust (or A Trust) and the Bypass Trust (or B Trust). Upon the death of the first spouse, assets equal to the estate tax exemption are transferred into the Bypass Trust, while the remaining assets go into the Marital Trust or directly to the surviving spouse. This split allows both spouses’ exemptions to be used separately.

Function and Tax Treatment

The assets placed in the Bypass Trust are no longer considered part of the surviving spouse’s estate for tax purposes. This means that when the second spouse dies, the trust assets are “bypassed” for estate tax calculations. However, the surviving spouse may still benefit from the trust during their lifetime. The Bypass Trust can provide income to the surviving spouse and may also allow discretionary distributions of principal for health, education, maintenance, and support (often referred to as HEMS standards).

Importantly, because the Bypass Trust is irrevocable and not part of the surviving spouse’s estate, it does not qualify for the marital deduction — a tax provision that allows unlimited tax-free transfers between spouses. Instead, the trust uses the deceased spouse’s exemption to shield assets from estate tax. The result is that the Bypass Trust is taxed separately, and while income generated by trust assets is taxable, the principal itself is excluded from estate taxation upon the second death.

Portability and Relevance Today

The Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 introduced portability, which allows a surviving spouse to use any unused estate tax exemption of their deceased spouse. This change led to a shift in how estate planners use Bypass Trusts. With portability in place, it is no longer strictly necessary to establish a Bypass Trust to preserve both spouses’ exemptions. Instead, the surviving spouse can elect to claim the deceased spouse’s unused exemption by filing a timely estate tax return.

Despite the availability of portability, Bypass Trusts remain relevant in many cases. Portability does not apply to generation-skipping transfer (GST) tax exemptions, which are not automatically transferrable. In families with significant wealth, asset appreciation, or a desire to protect assets from remarriage, creditors, or beneficiaries' financial mismanagement, Bypass Trusts provide a level of control and asset protection that portability cannot offer.

Advantages and Considerations

Using a Bypass Trust can help families reduce or eliminate federal estate taxes across two generations, especially when the estate is projected to grow. It also allows for multigenerational planning by designating how remaining assets should be distributed after the surviving spouse’s death.

However, there are trade-offs. Because assets placed in a Bypass Trust are not included in the surviving spouse’s estate, they do not receive a step-up in basis at the second spouse’s death. This can lead to higher capital gains taxes if appreciated assets are sold by heirs. Additionally, trust administration can be complex and may involve ongoing legal, accounting, and tax costs.

Another consideration is flexibility. Since the Bypass Trust is irrevocable, changes cannot be made once it is funded, which can become a challenge if family dynamics or financial needs change significantly over time.

Common Use Cases

Bypass Trusts are most commonly used by:

• High-net-worth couples seeking to minimize estate taxes.
• Families where asset protection from creditors or future spouses is a priority.
• Individuals who want to ensure children from a previous marriage inherit certain assets.

In blended families, the Bypass Trust can ensure that assets eventually pass to children from the first marriage, while still providing support to a surviving spouse.

The Bottom Line

A Bypass Trust is a foundational estate planning tool designed to preserve wealth by using the estate tax exemption of the first spouse to die. While portability has made it less essential in smaller estates, Bypass Trusts continue to offer strategic benefits, especially for large or complex estates, blended families, or those seeking multigenerational asset protection. Proper implementation requires coordination with estate planning professionals and a clear understanding of the family’s goals, tax exposure, and distribution preferences.