The 3.8% investment income tax on a large gain: when it starts and how much it adds
Federal tax
A married couple with $150,000 of other income and a $250,000 long-term gain pays $37,500 of income tax on the gain and $5,700 of the 3.8% tax: $43,200 in all.
- $5,7003.8% tax
- $43,200federal total
How the surcharge applies
The net investment income tax adds a surcharge to standard income tax. It applies to the lesser of your investment income or the amount exceeding a fixed threshold for your filing status. The key figures above show this calculation for a married couple. Their other income places them above the threshold, so the tax hits the full gain. This results in the specific surcharge shown. The total federal liability combines this surcharge with the standard income tax on the gain. Readers should note that the threshold is a fixed dollar amount set by law. It does not adjust for inflation automatically. This means more taxpayers may become subject to the tax over time as incomes rise. The calculation remains simple: identify the excess income, compare it to investment income, and apply the rate to the smaller figure.
| Other income ($) | Income tax on the gain ($) | 3.8% tax ($) |
|---|---|---|
| 50,000 | 25,335 | 1,900 |
| 150,000 | 37,500 | 5,700 |
| 250,000 | 37,500 | 9,500 |
| 400,000 | 37,705 | 9,500 |
Reading the table columns
The table above breaks down the components of the total tax. The first column lists other income, which determines if the threshold is crossed. The second column shows the standard income tax on the capital gain. The third column isolates the net investment income tax surcharge. Comparing these columns reveals how the surcharge stacks on top of existing liabilities. For the example provided, the surcharge is a distinct addition to the income tax. It is not a replacement or a deduction. The total in the lead combines these two elements. Each column serves a specific purpose in illustrating the cumulative effect of these federal taxes on investment gains.
Exclusions and thresholds
Not all gains count toward this calculation. Gain excluded on the sale of a main home does not count as investment income for this purpose. This exclusion prevents double taxation on primary residence sales. The threshold itself is fixed in law and does not index to inflation. Consequently, the number of households subject to the tax may grow without legislative changes. The current tax year rules apply as stated. Readers must check their specific filing status to find the correct threshold. The surcharge applies only to the portion of income above that limit. If investment income is lower than the excess income, the tax applies to the investment income instead. This logic ensures the tax targets investment returns specifically.
Estimates and context
All figures presented are estimates for the specific example provided. They reflect current tax year rules for the stated filing status and income levels. These numbers illustrate how the surcharge interacts with standard income tax. They do not guarantee identical results for every taxpayer. Individual circumstances vary based on deductions, credits, and other income sources. The table above summarizes the calculation for clarity. Use the capital gains tax calculator to model different scenarios. The methodology behind these estimates is detailed on the methodology page. For deeper details on the surcharge itself, consult the net investment income tax section. These resources provide context for the figures shown here.
Questions
Does the threshold change every year?
No. The threshold is fixed in law and does not automatically adjust for inflation. This means more taxpayers may become subject to the tax as incomes rise over time.
Which income amount determines the tax?
The tax applies to the lesser of your investment income or the amount exceeding the fixed threshold. This ensures the surcharge targets investment returns specifically rather than all income.
Are home sale gains included?
No. Gain excluded on the sale of a main home does not count as investment income for this calculation. This exclusion helps avoid double taxation on primary residences.
How is the total tax calculated?
The total combines standard income tax on the gain with the net investment income tax surcharge. The table above shows these components separately to illustrate the cumulative effect.
Every figure on this page is computed by code from the 2026 federal brackets and capital gains thresholds (IRS Rev. Proc. 2025-32) and the 2026 state brackets. See the methodology.