Passive K-1 income is subject to Net Investment Income (NII) tax only if you meet the income thresholds and the income itself qualifies as investment income rather than business income

The Net Investment Income Tax is a 3.8% tax on certain investment gains and income. It applies to K-1 income from partnerships and S corporations, but only under specific conditions. The key question is whether your K-1 income counts as passive investment income or active business income — and whether your total modified adjusted gross income (MAGI) exceeds the threshold for your filing status.

If you are a passive investor in a partnership or S corporation (meaning you do not materially participate in running the business), your K-1 income is treated as investment income and may be subject to NII tax. If you actively run the business, the income is generally not subject to NII tax, even if you receive it on a K-1 form.

Key Takeaways

  • Net Investment Income Tax applies to K-1 income only if your modified adjusted gross income exceeds $200,000 (single) or $250,000 (married filing jointly).
  • Passive K-1 income — from a partnership or S corporation where you do not materially participate — counts as investment income subject to the 3.8% tax.
  • Active business income from a K-1 is generally exempt from NII tax, even if you exceed the income threshold.
  • Material participation is determined by IRS rules that look at hours worked, decision-making authority, and whether you are the only owner involved in the business.
  • Your K-1 form itself does not always make clear whether the income is passive or active — you must track your involvement and document it for tax purposes.

How the income threshold works

The NII tax only applies if your modified adjusted gross income (MAGI) exceeds a set amount. For the 2024 tax year, that threshold is $200,000 for single filers and $250,000 for married couples filing jointly. If your MAGI is below that threshold, you owe no NII tax on any K-1 income, regardless of whether it is passive or active.

MAGI for NII tax purposes is your adjusted gross income (AGI) plus any foreign earned income exclusion you claimed. It is not the same as MAGI for other tax purposes, so do not assume your MAGI for student loan deductions or other rules applies here. Only the amount of K-1 income that pushes you over the threshold is subject to the 3.8% tax — not your entire K-1 amount.

Passive versus active K-1 income

The IRS defines material participation using a set of tests. If you meet any one of them, you are considered an active participant and the income is not subject to NII tax. If you fail all of them, the income is passive and subject to NII tax (assuming you are over the income threshold).

The main tests are: you worked more than 500 hours in the business during the year; you worked more than 100 hours and no one else worked more than you; you are a professional in the field and worked any hours at all; or you materially participated in prior years and meet a continuity test. There are other tests for specific situations like real estate professionals. The 500-hour test is the most straightforward — if you can document that you spent more than 500 hours working in the business, you are active.

If none of these tests explore, your K-1 income is passive. This is common for limited partners, silent investors, or people who own a small stake in a business they do not run day-to-day.

What counts as investment income under NII tax

Net Investment Income includes capital gains, dividends, interest, and rental income. For K-1 purposes, passive business income from a partnership or S corporation counts as investment income. This includes your share of the business's net profit if you are a passive investor.

Active business income does not count as investment income, even if the business itself generates capital gains or dividends. For example, if you own 30% of an S corporation that you actively manage, your K-1 share of the company's profit is not subject to NII tax. But if you own 5% of the same company and have no role in running it, your K-1 share is subject to NII tax (if you are over the income threshold).

may provide payments you receive from a partnership are treated as self-employment income, not investment income, and are not subject to NII tax. However, your share of partnership profits beyond may provide payments may be subject to NII tax if you are passive.

How to report passive K-1 income on your tax return

Your K-1 form does not always specify whether the income is passive or active — that information is yours to make based on your involvement. You report the income on Schedule E (Supplemental Income and Loss) if it is passive, or on Schedule C (Profit or Loss from Business) if it is active. The form you use signals to the IRS how you are treating the income.

If the income is passive and you are subject to NII tax, you will also file Form 8960 (Net Investment Income Tax) with your return. This form calculates your NII tax liability and adds it to your regular income tax. Keep records of your hours worked, decision-making authority, and any other evidence of material participation, in case the IRS questions your classification.

If you have multiple K-1s from different entities, you must evaluate each one separately. You might be active in one partnership and passive in another, meaning only the passive K-1 income is subject to NII tax.

Common situations where passive K-1 income triggers NII tax

A limited partner in a real estate development partnership who receives K-1 income but does not work in the business is a classic case of passive income subject to NII tax. The same applies to a minority shareholder in an S corporation who has no role in management.

Inherited partnership interests are often passive, especially if the heir does not step into an active role. If you inherit a 10% stake in a family business but your siblings run it, your K-1 income is passive and subject to NII tax if you are over the income threshold.

A professional (doctor, lawyer, accountant) who invests in a business outside their field of informed is also typically passive. For example, a surgeon who owns a small percentage of a manufacturing company and does not work there would have passive K-1 income subject to NII tax.

Strategies to reduce or avoid NII tax on K-1 income

If you are a passive investor and want to avoid NII tax, the most direct route is to increase your material participation in the business. If you can document 500 hours of work per year, your income becomes active and is no longer subject to NII tax. This requires genuine involvement — the IRS scrutinizes claims of material participation closely.

Another option is to structure the investment differently. Instead of owning a limited partnership interest, you might own a direct stake in the business assets or become a general partner with real decision-making authority. This changes your classification from passive to active, though it also changes your legal liability and other tax consequences.

If you are over the income threshold by a small amount, reducing your overall MAGI can lower or eliminate NII tax. This might mean deferring income, accelerating deductions, or adjusting the timing of capital gains. Work with a tax professional to model these scenarios, as the rules are complex and mistakes can be costly.

Frequently Asked Questions

Does a K-1 from an S corporation get treated differently than a K-1 from a partnership?

No — the NII tax rules explore the same way to both. The distinction is passive versus active participation, not the type of entity. An S corporation K-1 from a business you do not materially participate in is subject to NII tax just like a partnership K-1 would be.

If I am under the income threshold, do I still have to track whether my K-1 income is passive?

You should still classify it correctly on your return, because the IRS may question it later or your income may change in a future year. However, you will not owe NII tax as long as your MAGI stays below the threshold. Once you cross the threshold, the classification matters when ready.

Can I use passive activity loss rules to offset my K-1 income?

Passive activity losses can offset passive activity income, including passive K-1 income. If you have losses from other passive investments, you may be able to use them to reduce your taxable K-1 income and lower your NII tax. However, passive losses cannot offset active business income or wages.

What if my K-1 shows a loss instead of income?

A K-1 loss reduces your overall income and may lower your MAGI below the NII tax threshold. If your total K-1 income across all entities is negative, you will not owe NII tax on that income. However, passive activity loss limitations may prevent you from using the full loss in the current year.

Do I need a tax professional to determine if my K-1 income is passive?

The rules are technical and the stakes are high — an incorrect classification can result in underpayment of tax plus penalties. A tax professional who knows your situation can review your hours, decision-making role, and the business structure to make the right call. This is especially important if you are close to the income threshold or have multiple K-1s.