Quick Answer
The Net Investment Income Tax (NIIT) is a 3.8% tax on investment income for individuals earning over $200,000 (single) or $250,000 (married filing jointly). It applies to interest, dividends, capital gains, and rental income. In 2024, approximately 2.9% of taxpayers paid NIIT, generating $48 billion in revenue.
Best Answer
Sarah Chen, CPA
Best for taxpayers with significant investment income and high W-2 wages
What is the Net Investment Income Tax?
The Net Investment Income Tax (NIIT) is a 3.8% surtax that applies to the lesser of: (1) your net investment income, or (2) the amount your modified adjusted gross income (MAGI) exceeds the threshold. The thresholds are $200,000 for single filers and $250,000 for married filing jointly.
NIIT was enacted in 2013 as part of the Affordable Care Act to help fund Medicare. According to IRS Statistics of Income data, about 2.9% of taxpayers paid NIIT in 2024, with an average tax of $16,500 per affected return.
What counts as net investment income?
Net investment income includes:
It does NOT include:
Example: $300,000 salary with $50,000 investment income
Let's say you're single, earn $300,000 in salary, and have $50,000 in investment income (dividends and capital gains).
If your investment income had been $200,000 instead, you'd pay NIIT on $150,000 (the excess over the threshold), resulting in $5,700 in NIIT.
How NIIT affects your withholding strategy
NIIT is not subject to payroll withholding like regular income tax. You need to account for it through:
1. Increased W-4 withholding - Add extra federal tax withholding to cover the estimated NIIT
2. Quarterly estimated payments - Make payments directly to the IRS
3. Year-end tax planning - Harvest losses or defer gains to manage the tax
Key factors that affect NIIT liability
What you should do
If you expect significant investment income and your total income exceeds the thresholds, calculate your estimated NIIT liability and adjust your withholding accordingly. The W-4 optimizer can help you determine the right additional withholding amount to avoid underpayment penalties.
Key takeaway: NIIT adds 3.8% to your effective tax rate on investment income when your total income exceeds $200K/$250K, potentially costing thousands in additional taxes that aren't automatically withheld from paychecks.
Key Takeaway: NIIT adds 3.8% to your effective tax rate on investment income when your total income exceeds $200K/$250K, potentially costing thousands in additional taxes that aren't automatically withheld from paychecks.
NIIT thresholds and calculation examples for different income levels
| Filing Status | Income Threshold | Example Income | Investment Income | NIIT Owed |
|---|---|---|---|---|
| Single | $200,000 | $220,000 | $30,000 | $760 (20K × 3.8%) |
| Single | $200,000 | $300,000 | $50,000 | $1,900 (50K × 3.8%) |
| Married Filing Jointly | $250,000 | $280,000 | $40,000 | $1,140 (30K × 3.8%) |
| Married Filing Jointly | $250,000 | $400,000 | $80,000 | $5,700 (150K × 3.8%) |
More Perspectives
Marcus Rivera, CFP
Best for taxpayers with W-2 income from multiple employers plus investment income
Why multiple job holders need to understand NIIT
If you work multiple jobs and have investment income, NIIT calculations become more complex because your combined W-2 income from all employers counts toward the income threshold, but none of your employers withhold for NIIT.
Example: Two jobs plus investment income
Suppose you have:
Your total MAGI is $240,000, which exceeds the $200,000 single filer threshold by $40,000. Since your net investment income ($30,000) is less than the excess ($40,000), you owe NIIT on the full $30,000 of investment income: $30,000 × 3.8% = $1,140.
Neither employer withholds for this $1,140 NIIT liability because they don't know about your other income sources.
Withholding strategy with multiple jobs
You have three options to cover NIIT:
1. Increase withholding at your higher-paying job - Use Form W-4 Line 4(c) to add extra withholding
2. Make quarterly estimated payments - Pay the IRS directly four times per year
3. Combination approach - Some extra withholding plus estimated payments
The extra withholding approach is often simpler because it's automatic and counts toward safe harbor rules for avoiding underpayment penalties.
Key takeaway: With multiple jobs, your combined income might trigger NIIT even when individual job incomes seem modest, requiring proactive withholding adjustments since no single employer will withhold for the full tax liability.
Key Takeaway: With multiple jobs, your combined income might trigger NIIT even when individual job incomes seem modest, requiring proactive withholding adjustments since no single employer will withhold for the full tax liability.
Sarah Chen, CPA
Best for typical employees wondering if NIIT affects them
When W-2 employees need to worry about NIIT
Most W-2 employees don't owe NIIT because either their income is below the thresholds ($200K single/$250K married) or they don't have significant investment income. However, you might owe NIIT if you:
Quick NIIT check
Add up your expected:
If the total exceeds $200K (single) or $250K (married), and you have investment income, you might owe NIIT.
Example: $175,000 salary + $40,000 stock sale
You earn $175,000 in W-2 wages and sell stock for a $40,000 capital gain. Your total income is $215,000, which exceeds the $200,000 threshold by $15,000. You'll owe NIIT on $15,000 (the lesser of the excess income or investment income): $15,000 × 3.8% = $570.
This $570 won't be withheld from your paycheck, so you need to make an estimated payment or increase W-4 withholding.
Key takeaway: Most W-2 employees don't owe NIIT, but those with income near $200K should watch for large capital gains or other investment income that could trigger the 3.8% tax.
Key Takeaway: Most W-2 employees don't owe NIIT, but those with income near $200K should watch for large capital gains or other investment income that could trigger the 3.8% tax.
Sources
- IRS Publication 550 — Investment Income and Expenses
- IRS Form 8960 Instructions — Net Investment Income Tax
Related Questions
Reviewed by Sarah Chen, CPA on February 28, 2026
This content is for educational purposes only and is not a substitute for professional tax advice. Consult a qualified tax professional for advice specific to your situation.