Could You Owe the NIIT?
Selling appreciated investments, collecting rental income, or realizing a large capital gain can create unexpected tax consequences. Even if you have already calculated your regular capital gains tax, there may be another tax to consider: the Net Investment Income Tax (NIIT).
The NIIT is an additional 3.8% federal tax that may apply to certain investment income when your income exceeds specific thresholds. For high-income individuals, a large investment sale or other year-end financial transaction could push income above those thresholds and increase the overall tax bill.
Understanding how the NIIT works before making major financial decisions can help you identify planning opportunities, manage your tax exposure, and protect more of your investment returns.
Understanding the 3.8% Net Investment Income Tax
The NIIT generally applies to individuals whose modified adjusted gross income (MAGI) exceeds the applicable threshold and who have net investment income.
The tax is calculated at 3.8% of the lesser of your net investment income or the amount by which your MAGI exceeds the applicable threshold.
2026 NIIT Income Thresholds
The thresholds depend on your federal tax filing status.
Single or head of household: $200,000
Married filing jointly: $250,000
Married filing separately: $125,000
These thresholds are not indexed for inflation, which means they have remained fixed even as wages, investment values, and living costs have increased.
As a result, taxpayers who previously stayed below the threshold may become subject to the NIIT as their income grows.
What Counts as Net Investment Income?
Not every type of income is subject to the NIIT. The tax generally applies to certain investment income, including:
Taxable interest
Dividends
Capital gains from selling investments
Rental income
Royalties
Certain annuity income
Income from passive business activities
Certain deductions and expenses directly associated with investment income may reduce the amount subject to the tax.
What Income Is Generally Excluded?
Wages, Social Security benefits, and income from businesses in which you materially participate are generally not included in net investment income.
However, these income sources may still affect your MAGI.
That distinction is important: income that is not itself investment income can push your MAGI above the threshold, potentially exposing some of your investment income to the NIIT.
How a Year-End Windfall Can Trigger the NIIT
One of the biggest risks arises when a taxpayer receives a substantial amount of income in a single year.
You might normally earn less than the NIIT threshold, but a large capital gain could push your MAGI above it.
Example Scenario
Suppose you are a single taxpayer with the following financial information for 2026:
Salary: $150,000
Net investment income from a stock sale: $100,000
Assumed MAGI: $250,000
Your MAGI exceeds the $200,000 threshold by $50,000.
The NIIT applies to the lesser of:
Net investment income of $100,000
MAGI exceeding the threshold by $50,000
In this example, the NIIT would be $1,900, calculated as 3.8% of $50,000.
This amount would be in addition to any regular federal income tax owed on the investment gain.
The example assumes the stated amounts represent the relevant MAGI and net investment income figures after applicable adjustments. Actual calculations can differ depending on your deductions, filing status, and other financial circumstances.
Four Strategies to Help Manage Your NIIT Exposure
Although the NIIT cannot always be avoided, year-end planning may help reduce its impact. The right strategy depends on your financial goals, income projections, and investment circumstances.
1. Evaluate the Timing of Investment Sales
If you are planning to sell an appreciated stock, investment property, or another asset, consider how the timing will affect your income for the year.
For example, if you expect your income to be lower in 2027, delaying a sale until January may help reduce your NIIT exposure compared with recognizing the gain in 2026.
For real estate transactions, an eligible installment sale may allow you to recognize qualifying gain over multiple years as payments are received. However, installment reporting does not automatically eliminate NIIT, and special rules may apply.
Before postponing a sale, consider market conditions, cash-flow needs, transaction costs, and your overall investment strategy.
2. Consider Tax-Loss Harvesting
If you have realized capital gains during 2026, selling investments that have declined in value may help offset those gains.
For example, suppose you have $30,000 in realized capital gains and realize a $10,000 capital loss by selling another investment.
Subject to applicable tax rules, the loss may reduce your net capital gain to $20,000.
Reducing taxable capital gains may also reduce net investment income and potentially lower your NIIT liability.
However, you should review the wash sale rules before repurchasing a security sold at a loss. Tax-loss harvesting should also fit your investment objectives rather than being driven by tax considerations alone.
3. Review Opportunities to Reduce MAGI
Certain adjustments that reduce your adjusted gross income may also reduce MAGI for NIIT purposes.
Depending on your circumstances, potential planning opportunities may include:
Making eligible traditional 401(k) contributions
Making deductible traditional IRA contributions when eligible
Contributing to a Health Savings Account if you qualify
Reviewing other eligible adjustments to income
For 2026, the employee contribution limit for most traditional 401(k) plans is $24,500, subject to plan rules and applicable catch-up contribution provisions.
However, not every deduction reduces NIIT-related MAGI. Itemized deductions such as charitable contributions and mortgage interest generally do not directly reduce the MAGI calculation used for the NIIT.
Likewise, a traditional IRA contribution is deductible only when the applicable requirements are met. Eligibility for the deduction depends on factors such as income, filing status, and workplace retirement plan coverage.
A tax professional can help determine which adjustments are available and whether they would meaningfully reduce your exposure.
4. Coordinate Investment Decisions With Your Overall Tax Plan
A large investment sale should not be evaluated in isolation.
Before executing a significant transaction, review your projected income, existing gains and losses, retirement contributions, charitable plans, and potential tax obligations.
For example, selling appreciated investments in the same year as a business sale or another major financial event may produce a different tax outcome than completing those transactions in separate years.
Coordinating these decisions can help you avoid unexpected tax liabilities and identify opportunities to manage your income across multiple tax years.
Why Planning Matters
The NIIT can add a meaningful amount to your tax bill, particularly when a large investment gain pushes your MAGI above the applicable threshold.
Waiting until you prepare your tax return may leave you with limited opportunities to change the outcome.
Before the end of 2026, consider reviewing:
Your projected modified adjusted gross income
Your realized and unrealized capital gains and losses
Potential investment sales before year-end
Rental and passive business income
Eligible retirement plan contributions
Potential installment sale opportunities
Your estimated federal tax payments
The combined effect of regular income tax, capital gains tax, and NIIT
Tax planning should support your financial objectives, not dictate every investment decision. Selling an asset solely to reduce taxes may not make sense if it conflicts with your long-term investment strategy.
Conclusion
The Net Investment Income Tax is an important consideration for high-income investors, business owners, and taxpayers expecting a significant financial windfall.
Because the NIIT can apply on top of regular income and capital gains taxes, overlooking it may lead to an unexpectedly large tax bill. Reviewing your income projections, timing investment sales carefully, harvesting losses when appropriate, and evaluating eligible income adjustments may help you manage your exposure.
Before you sell a highly appreciated investment or complete a major transaction, contact Guerrero CPA at 210-490-7100. Our team can help project your MAGI, calculate your potential NIIT liability, and evaluate tax-planning strategies that align with your broader financial goals.