For decades, the Credit Shelter Trust, often called an AB Trust or Bypass Trust, was a cornerstone provision built into the Revocable Living Trust for married couples. If you were a married couple with a net worth over a few hundred thousand dollars, your estate attorney likely advised you to include these AB provisions. It was the golden standard for avoiding federal estate taxes.
However, tax laws have changed dramatically. What was once essential planning has, for many families, become unnecessary complexity. Tax laws in 2026 are vastly different from those in 1995, 2005, or even 2015. If your trust was drafted before 2018, keeping an outdated AB Trust structure in place can create administrative burdens, reduce tax efficiency, limit flexibility for the surviving spouse, and potentially cost your heirs thousands.
This article explains why many married couples should review, and often remove, the Credit Shelter Trust provisions from their revocable living trust.
The Original Purpose of the Credit Shelter Trust
When planning with a Credit Shelter Trust, each spouse had a separate federal estate tax exemption, and unused exemption amounts were lost when the first spouse died. This created a major risk: if all assets passed outright to the surviving spouse, the first spouse’s exemption could be wasted, potentially resulting in significant estate taxes later.
The AB Trust solved this problem by dividing the trust into two parts upon the first death:
- Trust A (Survivor’s Trust): The surviving spouse’s share, fully revocable and controllable.
- Trust B (Credit Shelter / Bypass Trust): The deceased spouse’s share, irrevocable and designed to use that spouse’s estate tax exemption.
This ensured both spouses’ exemptions were preserved. At the time, this planning was essential because exemptions were relatively low, sometimes as low as $600,000.
The Game-Changing Concept: Portability
The federal law introduced portability, allowing a surviving spouse to use the unused estate tax exemption of the deceased spouse. This fundamentally changed estate planning. A married couple can now protect over $30 million in 2026 from federal taxes without needing a complex, restrictive AB Trust. For a full breakdown of current exemption amounts and how the law changed, see our 2026 estate tax law updates for California families.
Today, a surviving spouse can simply elect portability by filing an estate tax return, preserving both spouses’ exemptions without needing a Credit Shelter Trust.
As of 2026, the federal estate tax exemption remains historically high, meaning most married couples will never owe federal estate tax. For many families, the AB Trust has become a solution to a problem that no longer exists.
The Hidden Downsides of Keeping an AB Trust
While AB Trusts still serve a purpose in certain high-net-worth or special-circumstance situations, they often create unintended disadvantages for typical families.
1. Loss of Second Step-Up in Basis
One of the most significant drawbacks involves capital gains taxes.
When the first spouse dies, assets receive a step-up in basis to fair market value. However, assets placed in the Credit Shelter Trust do not receive another step-up when the surviving spouse dies.
This can result in large capital gains taxes for heirs.
Without an AB Trust, assets included in the surviving spouse’s estate typically receive a second step-up, potentially eliminating capital gains taxes entirely. For families with appreciating assets, especially real estate in high-growth areas, this difference can save heirs hundreds of thousands of dollars.
2. Increased Administrative Burden
When the Credit Shelter Trust is triggered, the surviving spouse must:
- Divide assets between subtrusts
- Maintain separate accounting
- File separate tax returns for the irrevocable trust
- Potentially hire attorneys and CPAs annually
- Manage stricter legal fiduciary duties
This adds ongoing cost and complexity during an already difficult time. Many surviving spouses find this structure confusing and restrictive.
3. Reduced Flexibility for the Surviving Spouse
Assets in the Credit Shelter Trust are no longer fully controlled by the surviving spouse. The surviving spouse must follow specific trust terms and may face limits on:
- Distributions
- Investment decisions
- Changing beneficiaries
- Selling or transferring certain assets
While designed for protection, these restrictions can create unnecessary rigidity.
4. Higher Income Tax Rates Inside Trusts
Irrevocable trusts reach the highest federal income tax brackets at extremely low income levels compared to individuals. This means trust income may be taxed at higher rates than if assets were owned outright by the surviving spouse.
5. Outdated Planning for Today’s Exemption Levels
Even with anticipated future reductions in the federal estate tax exemption, most couples still fall well below taxable thresholds. Maintaining an AB Trust “just in case” often imposes real costs today for a risk that may never materialize.
Situations Where a Credit Shelter Trust May Still Be Appropriate
AB Trusts are not obsolete in every case. They may still be beneficial when:
- The couple’s estate significantly exceeds projected estate tax exemptions
- There are children from prior marriages
- Asset protection from creditors is a primary concern
- There are concerns about remarriage
- State estate taxes apply at lower thresholds
- Special needs planning is involved
Estate planning should always be individualized. If your estate may fall into one of these categories, our High Net Worth Planning page outlines the advanced strategies, including irrevocable trusts and Credit Shelter provisions, that may still benefit larger, more complex estates.
A Simpler Modern Alternative
Many married couples now use a joint revocable living trust with portability-based planning, sometimes combined with flexible provisions that allow a Credit Shelter Trust to be created only if necessary. This approach provides:
- Simplicity during administration
- Maximum flexibility
- Potential for a full step-up in basis
- Lower administrative costs
- Continued tax protection if laws change
The Risk of Doing Nothing
Thousands of married couples still have AB Trust provisions written decades ago. If the first spouse dies and the trust automatically splits, the surviving spouse may be locked into a structure that is difficult, expensive, and tax-inefficient to unwind.
Reviewing and modernizing the trust before it becomes irrevocable is far easier, and far less costly, than addressing it after the fact.
When to Review Your Trust
You should review your estate plan if:
- Your trust was created before 2013
- Your net worth is below federal estate tax thresholds
- Your primary assets are a home and investment accounts
- You want to simplify administration for your spouse
- You have moved to a different state
- You have not reviewed your trust in over five years
Estate planning documents should evolve with tax law and personal circumstances.
Frequently Asked Questions
| Question | Answer |
| What is a Credit Shelter Trust? | An irrevocable sub-trust created upon the first spouse’s death, designed to preserve the deceased spouse’s estate tax exemption. It is also called an AB Trust or Bypass Trust. It divides the marital trust into a Survivor’s Trust (Trust A) and a Credit Shelter Trust (Trust B). |
| Do I still need an AB Trust in 2026? | For most married couples, no. Federal portability allows a surviving spouse to use the deceased spouse’s unused exemption without a Credit Shelter Trust. With the 2026 exemption at $15 million per person ($30 million per couple), the vast majority of California families will never face federal estate tax. |
| What happens if I do not remove the AB provisions? | When the first spouse dies, the trust automatically splits. The surviving spouse may be locked into a complex, restrictive, and tax-inefficient structure. Assets in the Credit Shelter Trust will not receive a second step-up in basis, potentially creating large capital gains taxes for your heirs. |
| Can I remove AB Trust provisions from my existing trust? | Yes, but only while both spouses are alive and mentally competent. Once the first spouse passes, the Credit Shelter Trust becomes irrevocable and amendments are generally not possible. Acting before that event is critical. |
| How do I know if my trust has AB provisions? | Review your trust document for references to a “Credit Shelter Trust,” “Bypass Trust,” or language describing a split into “Marital” and “Survivor’s” sub-trusts triggered upon the first spouse’s death. An estate planning review with David is the most reliable way to confirm this. |
The Credit Shelter Trust was once essential for married couples seeking to avoid estate taxes. Today, due to portability and historically high exemptions, it is often unnecessary and may even create tax disadvantages and administrative burdens.
Modernizing a revocable trust by removing or making the AB Trust optional can simplify administration, improve tax outcomes, and provide greater flexibility for the surviving spouse and heirs. A proactive estate planning review ensures that your trust reflects current law, not outdated assumptions from decades past.
| Is It Time to Update Your Trust? If your trust was drafted before 2018, it may contain AB Trust provisions that no longer serve your family’s best interests. David Schneider has helped thousands of Southern California families modernize their estate plans for today’s tax landscape. Schedule your free, no-obligation consultation today by calling (805) 374-8777, or contact us online to get started. People do not plan to fail, but they do often fail to plan. Let David help ensure your trust is working for your family, not against it. |