US Trust & Estate Income Tax Calculator

What the trust estate income tax calculator does

The calculator estimates the federal tax a non-grantor trust or an estate owes on income it keeps instead of passing to beneficiaries. Enter the taxable income and, if relevant, the part that is net investment income. The tool returns the federal income tax, the 3.8% Net Investment Income Tax (NIIT), the total tax, the effective rate and the amount kept after tax. It is meant for fiduciaries, executors and advisors who want a quick view of the cost of holding income inside a trust or estate.

Trusts and estates are separate taxpayers. When a non-grantor trust earns interest, dividends, rent or capital gains and does not distribute them, it pays tax on that income itself, and its rates rise very quickly.

Why the brackets are so compressed

An individual reaches the top federal rate only at a high income. A trust or estate climbs the same rate ladder within a small fraction of that income, so retained trust income is taxed much more heavily than the same income earned by most individuals. The design discourages using trusts to shelter investment income at low rates and encourages fiduciaries to distribute income to beneficiaries, who pay tax at their own, often lower, rates.

Distributed income generally carries out to beneficiaries through a distribution deduction and is taxed on their returns. Accumulated income stays with the trust and is taxed at the compressed rates. Modeling the retained income shows the cost of accumulating it.

How the calculation works

• It applies the compressed federal brackets to the trust's taxable income, summing the tax owed in each band.
• It identifies the marginal rate, the rate applied to the last dollar of income.
• It calculates NIIT as 3.8% of the lesser of net investment income and the amount of taxable income above the top bracket threshold.
• It adds the income tax and NIIT to find the total tax, then subtracts that from taxable income to show what the trust keeps.

For individuals the NIIT threshold is a fixed amount; for a trust or estate it is the dollar amount where the top bracket begins. That figure is low, so investment income held in a trust can attract the 3.8% surtax at a modest income, another reason to consider distributing investment income to beneficiaries whose own thresholds are far higher.

Reading the results

The results show the federal income tax on retained income, the NIIT on undistributed investment income, and the total. The effective rate expresses the total as a percentage of taxable income, useful for comparing with the rate a beneficiary might pay. The marginal rate shows what another dollar of retained income would cost.

A trust that keeps a few thousand dollars sits in the lower bands, but the effective rate climbs quickly toward the top rate as retained income grows. When it approaches or exceeds a beneficiary's likely personal rate, distributing the income may reduce the family's overall tax.

Fiduciary planning

Distributing income lowers the trust's tax but hands cash and a tax bill to beneficiaries, which may conflict with the settlor's wish to build wealth in the trust or to protect a beneficiary from receiving funds. Retaining income keeps control in the trust at the cost of the compressed rates and the NIIT.

Distributions made within a set window after year-end can sometimes be treated as made in the prior tax year, so fiduciaries can act after the year closes. Capital gains are often, though not always, taxed to the trust and not carried out to beneficiaries, which is one reason retained investment income is common in trusts. These rules are detailed and depend on the facts.

This is an estimate for planning and education, not tax advice or a substitute for a prepared fiduciary income tax return. It covers federal tax only and does not address state taxation of trusts, the distribution deduction in detail, the alternative minimum tax, or special rules for particular trusts. Confirm the treatment of any specific trust or estate with a qualified tax professional.

About This Tool: Trust Estate Income Tax

Trust estate income tax: use this tool to get an instant, accurate estimate. The figures follow official IRS guidance and every rate and threshold is kept up to date for 2026. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.