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Why this happens
NIIT is a surtax on net investment income above income thresholds set by the IRS. Wages are not investment income, so the itself is generally outside NIIT.
When you sell shares after , any is investment income and can count toward NIIT if your income is high enough.
Dividends on shares you hold are also investment income for this purpose.
So with , NIIT is mostly a 'what happens after I hold and sell' question, not a 'what happens at ' question.
What to check
- Whether you sold shares after and realized .
- Dividends received on shares you held.
- Your modified adjusted gross income relative to the IRS thresholds for the year.
- How NIIT differs from additional Medicare tax (investment income vs. wages).
- Whether holding period made gains short- or long-term.
Common mistake
Example scenario (hypothetical)
Illustration only, not your tax situation.
When to get help from a tax pro
- You have large from selling appreciated shares.
- Your income is near the NIIT thresholds.
- You hold dividend-paying company stock.
- You want to coordinate sales across tax years.
Related calculators
Related pages
- RSUs and Medicare / Additional Medicare Tax
Large RSU vests can push wages over thresholds where additional Medicare tax may apply.
- RSU Ordinary Income vs Capital Gains
Most RSU tax at vest is ordinary income on your W-2; only price changes after vest may create capital gain or loss.
- RSU Tax Planning for High Earners
Large vests can push you into higher brackets. planning ahead beats scrambling when the vest hits payroll.
- RSU Tax Guide for High Earners
When RSUs are a large share of pay, withholding gaps and surtaxes deserve a deliberate plan.
For learning, not filing
Grants, employers, and states all differ. Use your own documents and a qualified tax professional before you make decisions from this guide.
