Bypass / Credit Shelter Trust Calculator 2026 β A-B Trust Estate Planning
Calculate estate tax savings from a Bypass (Credit Shelter) Trust vs portability vs no planning. Model Trust A and Trust B growth to the second death with 2026 exemption of $13.99M.
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$13.99M per person in 2026 (OBBBA extended) %
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Typically same as total estate at planning date $0
Estate Tax Saved vs No Planning
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Trust B Funded At
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Trust B Value at 2nd Death
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Estate Tax (Bypass Plan)
Strategy Comparison at Second Death
| Strategy | Estate at 2nd Death | Taxable Estate | Estate Tax | To Heirs |
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How to Use This Bypass Trust Calculator
Enter the combined estate value and how many years you expect between the first and second death. Trust B (bypass) is funded with assets up to the exemption amount at first death. Those assets grow separately and pass to heirs free of estate tax. The surviving spouse's Trust A (marital) gets the remaining estate and is included in the survivor's estate at death.
The Formula
Trust B = min(Estate at First Death, Exemption)
Trust A = Estate at First Death β Trust B
Trust B at Second Death = Trust B Γ (1 + growth)^years (estate-tax-free)
Trust A at Second Death = Trust A Γ (1 + growth)^years + survivor's own assets
Estate Tax (40%) applies only to Trust A above survivor's own exemption
Trust A = Estate at First Death β Trust B
Trust B at Second Death = Trust B Γ (1 + growth)^years (estate-tax-free)
Trust A at Second Death = Trust A Γ (1 + growth)^years + survivor's own assets
Estate Tax (40%) applies only to Trust A above survivor's own exemption
Example
$20M estate, 6% growth, 15 years between deaths, 2026 exemption $13.99M:
Trust B at first death: $13.99M | Trust A: $6.01M
Trust B grows to: $13.99M Γ 1.06^15 = $33.5M (zero estate tax)
Trust A grows to: $6.01M Γ 1.06^15 = $14.4M
Survivor's exemption: $13.99M | Trust A taxable: ~$0.4M Γ 40% = $168K
Total estate tax: ~$168K vs No Planning: ~$6.5M = Saved $6.3M
Trust B at first death: $13.99M | Trust A: $6.01M
Trust B grows to: $13.99M Γ 1.06^15 = $33.5M (zero estate tax)
Trust A grows to: $6.01M Γ 1.06^15 = $14.4M
Survivor's exemption: $13.99M | Trust A taxable: ~$0.4M Γ 40% = $168K
Total estate tax: ~$168K vs No Planning: ~$6.5M = Saved $6.3M
Extended
Two-Spouse Scenario Modeler & 3-Strategy Comparison
Adjust first death amount, growth rate, and years between deaths. Compare Bypass Trust vs Portability vs No Planning with SVG growth charts
Adjust all parameters and see how Trust A, Trust B, and each strategy perform at the second death date. Compare three estate planning strategies side-by-side.
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3-Strategy Comparison at Second Death
| Strategy | Estate Value | Taxable | Estate Tax | To Heirs | Tax Saved |
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Trust A + Trust B Growth Over Time
Frequently Asked Questions
What is a Bypass Trust (A-B Trust) and why use it?
A Bypass Trust β also called a Credit Shelter Trust or B Trust β uses the deceased spouse's federal estate tax exemption ($13.99M in 2026) at first death by funding a trust with assets up to that exemption. The trust grows estate-tax-free during the surviving spouse's lifetime and passes to heirs without being added to the survivor's taxable estate. The surviving spouse can receive income from Trust B and even principal in limited circumstances.
What is the difference between Bypass Trust and portability?
Portability (DSUEA) allows a surviving spouse to inherit the deceased spouse's unused exemption β but only the dollar amount, not the future appreciation. If the exemption is $13.99M today and assets in the bypass trust grow to $25M over 20 years, only the $25M appreciation escapes estate tax. With portability, you'd carry over $13.99M exemption but pay estate tax on all growth above that. Bypass trust is generally superior when significant asset appreciation is expected.
When does the estate tax exemption sunset?
Under current law (as extended by the OBBBA through 2030+), the federal estate tax exemption is $13.99M per person in 2026 (indexed for inflation). Prior to TCJA extension, the exemption was set to revert to approximately $7M in 2026. Any bypass trust funded today locks in the current exemption amount regardless of future legislative changes, which is a key planning advantage.
Can a Bypass Trust also use the GST exemption?
Yes. When funding the Bypass Trust, the planner can allocate GST exemption to it at the same time. This creates a "Dynasty-style" Trust B that can benefit not just children but grandchildren and beyond β all free of both estate tax and generation-skipping transfer tax. Each generation avoids the 40% estate tax and 40% GST tax that would otherwise apply to transfers to grandchildren.
Is a Bypass Trust still useful after portability was made permanent?
Yes, for several reasons: (1) Growth in the bypass trust escapes estate tax entirely; portability only shelters the exemption amount, not growth. (2) Bypass trusts offer asset protection from the survivor's creditors and new spouse. (3) Portability must be elected on a timely estate tax return β if the estate is non-taxable, many families skip filing, losing portability. (4) Some states (NY, MA, OR, WA) have estate taxes but no portability β bypass trust works there too.