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← No thanks, take me backCompanies typically withhold RSU income at a flat 22% federal rate, but your real marginal rate may be higher. See whether that gap puts you at risk of an IRS underpayment penalty.
This calculator covers federal income tax and Colorado state income tax only. If you live in or file taxes in another state, the state tax and state safe harbor figures below will not apply to you. Only the federal results will be relevant.
Enter shares and price per share for each vesting date this year. Use actual figures for any vest that has already happened, and your best estimate for any that haven't. Check the box for a vest if its withholding is already reflected in the "Federal / State Tax Withheld YTD" figures below; leave it unchecked and we'll estimate withholding at the rate you set.
Enter your income and RSU details to see your safe harbor status.
Your projected income and tax liability will appear here.
Most employers withhold a flat 22% federal rate on RSU vests. If your combined income pushes your marginal rate to 32%, 35%, or 37%, that flat rate falls short, and the gap grows every quarter it happens.
The IRS charges an underpayment penalty (effectively interest on the shortfall) if your withholding and estimated payments fall short of the "safe harbor" threshold during the year, even if you pay in full by April.
Increase your W-4 withholding on salary, elect extra withholding on future vests, or make a quarterly estimated tax payment before the next deadline, whichever fits your situation best.
2026 Tax Brackets & Standard Deductions. This calculator applies 2026 federal ordinary income tax brackets. Single filers: 10% ($0 to $12,400), 12% ($12,401 to $50,400), 22% ($50,401 to $105,700), 24% ($105,701 to $201,775), 32% ($201,776 to $256,225), 35% ($256,226 to $640,600), 37% ($640,601+). Married Filing Jointly: 10% ($0 to $24,800), 12% ($24,801 to $100,800), 22% ($100,801 to $211,400), 24% ($211,401 to $403,550), 32% ($403,551 to $512,450), 35% ($512,451 to $768,700), 37% ($768,701+). Standard deductions applied: Single $16,100; Married Filing Jointly $32,200. Safe harbor. You generally avoid an underpayment penalty if your withholding and timely estimated payments equal the smaller of 90% of your current-year tax or 100% of your prior-year tax (110% if your prior-year AGI exceeded $150,000, or $75,000 if married filing separately). This calculator checks both tests and uses whichever is lower. Colorado applies the identical safe harbor structure to state tax, which this calculator checks separately using the same tests. Additional Medicare Tax of 0.9% is applied to income above $200,000 (single) or $250,000 (MFJ). Long-term capital gains are taxed at your selected flat rate rather than the true tiered 0%/15%/20% thresholds; short-term gains are taxed as ordinary income. RSU withholding is only added for vests you mark as not yet withheld. For vests marked already withheld, that amount is assumed to already be included in the YTD totals you entered. This tool does not account for the Alternative Minimum Tax, the 3.8% Net Investment Income Tax, capital loss deduction limits, itemized deductions, the tax rules of any state other than Colorado, or the IRS's and Colorado's actual quarterly-compounded penalty rates. It estimates whether you are on track and the shortfall to close, not the exact dollar penalty either would assess. Tax laws are subject to change. This tool is for educational purposes only and does not constitute tax or financial advice. Consult a qualified tax advisor before making withholding or estimated payment decisions.
We help RSU earners plan withholding and estimated payments before it becomes a problem, not after the tax bill arrives.
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