RSU Tax Withholding: The Flat 22% and the Bill It Leaves Behind
Your employer withholds RSU vests at 22% while your real rate is probably 32% to 37%. Here is exactly how the withholding works, the worked math on the gap, and the fixes that beat the April surprise.
★ 5.0 on Google113 reviews1,000+ clientsAll 50 states, fully remote
Quick answer
When RSUs vest, the full market value is W-2 wage income, and employers withhold federal income tax at the flat supplemental rate: 22% until your supplemental wages for the year exceed $1 million, 37% beyond. If your salary plus vests puts you in the 32% to 37% bracket, every vested dollar is under-withheld by roughly 10 to 15 cents, and the fix is closing that gap with extra withholding or quarterly estimated payments.
The most common RSU tax problem is not exotic. Shares vest, payroll withholds exactly what the rules require, everything looks handled, and then the return comes up five figures short in April. The cause is a single mismatch: withholding runs at a flat 22% while the income itself is taxed at your marginal bracket, which for most people receiving meaningful RSUs is 32% to 37%. This page walks the mechanics, quantifies the gap with real 2026 numbers, and lays out the fixes in order of ease.
Worked case: a $300,000 salary plus $400,000 of RSUs
On a $400,000 vest, 22% withholding sends $88,000 to the IRS. With a $300,000 salary, a single filer pays about $141,000 of federal tax on that vest at 35% and 37%, leaving a gap near $53,000 before state tax. Close it before January 15, 2027: raise W-4 withholding for the rest of 2026 or make a fourth-quarter estimate that reaches the safe harbor.
| Line | Single | Married filing jointly, one earner |
|---|---|---|
| Taxable income before the vest | $283,900 | $267,800 |
| Brackets the vest fills | 35%, then 37% above $640,600 | 24%, 32%, then 35% |
| Federal tax on the $400,000 vest | about $140,900 | about $121,800 |
| Withheld at 22% | $88,000 | $88,000 |
| Gap before state tax | about $52,900 | about $33,800 |
Illustrative arithmetic using 2026 brackets and standard deductions ($16,100 single, $32,200 joint). Your return will differ.
How RSU Withholding Actually Works
Supplemental wages, one flat rate, no opinion about your bracket
When RSUs vest and shares are delivered, the market value of those shares that day is compensation, identical in character to salary, and it lands in Box 1 of your W-2. But payroll systems do not withhold on it the way they withhold on salary. RSU income is classified as supplemental wages, the same bucket as bonuses and commissions, and supplemental wages get their own withholding rules.
The rule nearly every employer uses: withhold a flat 22% of the supplemental payment for federal income tax, until your cumulative supplemental wages for the calendar year pass $1 million, at which point a mandatory 37% applies to the excess. The 22% is not tailored to you. It does not know your salary, your spouse's income, or your bracket. It is the same rate for an analyst with a $15,000 vest and a director with a $400,000 vest.
Mechanically, the withholding is usually funded by share withholding (the company keeps back enough shares to cover the tax deposit and delivers the net) or sell-to-cover (the broker sells enough shares at market and remits cash). Either way, the amount withheld is calibrated to the flat rate, so the method does not change the shortfall, only the mechanics.
What Payroll Withholds vs What You Actually Owe
The 10-to-15 point gap on every vested dollar becomes April's balance due
Payroll is following the rules. The rules just were not written for your bracket.
Map that against the 2026 brackets and the problem is visible from orbit. A single filer crosses into the 32% bracket at $201,775 of taxable income and 35% at $256,225. RSU income stacks on top of salary, so the vest itself is what pushes you into those brackets, where it is then taxed 10 to 13 points above what was withheld. The withholding system is not broken; it was simply never designed to be your final answer, and the W-2 wage base it uses makes the shortfall systematic rather than random.
The Full Withholding Stack: FICA, Additional Medicare, State
Income tax is the biggest line, not the only one
RSU vests are FICA wages too, and the payroll-tax layer behaves differently from the income-tax layer:
| Layer | Rate | How it applies to a vest |
|---|---|---|
| Federal income tax | 22% flat (37% over $1M supplemental) | The systematic under-withholding described above |
| Social Security | 6.2% | Only until total wages reach $184,500 (2026); late-year vests often owe none |
| Medicare | 1.45% | No cap; applies to every vested dollar |
| Additional Medicare | 0.9% | Withheld on wages above $200,000; owed above $200k single / $250k MFJ |
| State income tax | Varies | Flat supplemental rates that may lag your real state bracket |
Two quiet gotchas live in this stack. First, the Additional Medicare Tax thresholds do not match: employers withhold above $200,000 of wages per employer, but married couples owe it above $250,000 of combined wages, so two spouses each earning $150,000 plus RSUs can owe Additional Medicare Tax that nobody withheld. Second, state supplemental rates are their own patchwork; a California employee's default state withholding on RSUs, for example, may not match a high earner's actual top state rate, adding a state layer to the same federal story.
If your vests come from a still-private company waiting on an IPO, the timing is different but the gap is bigger: years of vesting can settle in one day. That scenario has its own page: double-trigger RSUs.
Holding ISOs alongside RSUs? Run the AMT calculator for ISO exercises before you exercise.
“I recently had the pleasure of working with Taxstra, and I must say, the experience exceeded my expectations. From start to finish, their professionalism, expertise, and customer care were outstanding.”
Published client feedback. Individual experiences vary.
The Worked Example: A $200,000 Vest Year
$150,000 salary, $200,000 of vests, one five-figure gap
Worked example (hypothetical, illustrative round numbers)
A single software engineer earns a $150,000 salary, and $200,000 of RSUs vest across the year. Payroll withholds federal income tax on the vests at the flat rate: 22% x $200,000 = $44,000, funded by sell-to-cover. Everything looks handled.
Now the actual tax on the RSU layer. Total income $350,000 minus the $16,100 standard deduction leaves $333,900 of taxable income; without the RSUs it would have been $133,900. The vest dollars fill the brackets from there: about $67,900 taxed at 24% ($16,300), $54,450 at 32% ($17,400), and the last $77,675 at 35% ($27,200). Federal tax on the vests: roughly $60,900, an average of about 30.5% against the 22% withheld.
Withheld: $44,000. Owed on the vests: about $60,900, plus roughly $1,350 of Additional Medicare Tax on the wages above $200,000 (partially withheld late in the year). Federal shortfall: roughly $17,000, before any state gap, surfacing as a balance due the following April, possibly with an underpayment penalty attached. Nothing went wrong. This is the system working as designed.
Your numbers will differ with filing status, state, and vest sizes, which is exactly what our free RSU tax calculator is for: enter salary and vest value, and it estimates the income, the flat withholding, your real marginal tax, and the shortfall in about thirty seconds.
Fixing the Gap: Four Tools, In Order of Ease
All four beat finding out in April
1. Aim at a safe harbor, not at perfection.
You do not need to nail your exact liability mid-year; you need to avoid the underpayment penalty. The safe harbors: total withholding plus timely estimates covering 90% of this year's tax, or 100% of last year's tax (110% if last year's AGI topped $150,000). In a rising-income year, the prior-year number is fixed and known, which makes 110% of it the cleanest target: hit it and the penalty is off the table regardless of how large April's balance turns out to be.
2. Add extra withholding to regular paychecks.
Form W-4, line 4c, lets you add a flat extra amount to every paycheck's withholding. Withholding has a superpower estimates lack: it is treated as paid evenly through the year no matter when it happens, so even a December W-4 change can cure earlier-quarter underpayment. Divide your estimated gap by remaining paychecks, submit the W-4, done. Some stock plan systems also allow electing a higher flat rate on the vests themselves; if yours does, that is the most direct fix.
3. Make quarterly estimated payments.
If W-4 changes are impractical, pay the gap directly at the quarterly deadlines (April 15, June 15, September 15, and January 15 of the following year) via IRS Direct Pay. Estimates are credited when paid, so match them to the quarters your vests actually land in if the amounts are lumpy.
4. Sell a slice of each vest for taxes, deliberately.
If you would not buy your company's stock with cash today, selling vested shares at delivery is rational anyway, and earmarking a tax slice (the gap between your marginal rate and 22%) turns each vest into its own funded tax event. There is minimal capital-gains cost to an immediate sale, since the basis equals the vest price you were just taxed on.
Common RSU Withholding Mistakes
The patterns behind most surprise bills
1. Treating sell-to-cover as "taxes handled."
Sell-to-cover funds the withholding, and the withholding is the flat 22%. The phrase sounds comprehensive and covers roughly two-thirds of a high earner's actual liability. The number of people who discover this via a five-figure balance due, rather than a paragraph like this one, is the reason this page exists.
2. Copying the 1099-B basis at filing time.
After a vest-and-sell, brokers commonly report a cost basis of zero or of some partial figure on Form 1099-B, because the reporting rules do not let them include your W-2 income in basis. File it unadjusted and you pay capital gains tax on wages you already paid tax on. The fix is a basis adjustment on Form 8949; the vest confirmation from your equity portal has the correct vest-date value. The same trap catches ESPP sellers every spring.
3. Holding every share and compounding the problem.
Holding vested shares means the tax gap must be paid from other cash while your net worth concentrates in one ticker. If the stock then falls, you owe full wage tax on the vest value with only a $3,000-per-year capital loss valve on the decline. Decide your hold-versus-sell policy once, in writing, and let it run.
4. Forgetting the state layer, especially after a move.
States source RSU income earned across a vesting period worked in multiple states, and default state withholding rarely matches that allocation. Move from a high-tax state mid-grant and both states may have a claim; move to one and your withholding may be pointed at the wrong state entirely. Flag any move on your vesting timeline for your preparer.
The penalty runs even if you pay in full by April 15
The estimated-tax penalty is interest-based and accrues quarter by quarter through the year. Paying your entire balance on April 15 does not erase it; only meeting a safe harbor during the year does. On a large gap, the penalty alone can run to four figures, which is expensive for a problem a W-4 line fixes.Vest-Year Planning Angles
Once the gap is handled, the actual planning starts
Use high-vest years for deductions that care about your bracket. Charitable contributions, and especially donor-advised fund bunching, are worth the most in the year your marginal rate peaks. A $30,000 contribution deducted at 35% beats the same contribution at 24% by $3,300 of federal tax.
Watch the thresholds a vest can trip. RSU income raises modified AGI for the 3.8% net investment income tax on your portfolio income ($200,000 single, $250,000 joint), and can push you across Medicare IRMAA cliffs that raise premiums two years later if you are near that horizon.
Coordinate RSU years with other equity events. A heavy vest year is generally the wrong year to also exercise nonqualified options (more supplemental income at the same too-low withholding), but it can be exactly the right year for an ISO exercise, because towering regular tax absorbs the AMT adjustment; the math lives in our ISO AMT guide. If you hold multiple equity types and are weighing them, start with RSUs vs stock options.
If vests recur every quarter and the numbers are large, this stops being a once-a-year cleanup and becomes an ongoing planning problem, which is what our stock compensation planning service exists for.
Frequently Asked Questions
RSU withholding, the shortfall, and the fixes
How much tax is withheld when RSUs vest?
Federal income tax is withheld at the flat supplemental rate: 22% until your supplemental wages for the calendar year pass $1 million, and a mandatory 37% on the excess. On top of that, Social Security tax (6.2%) applies until your total wages hit the 2026 wage base of $184,500, Medicare tax (1.45%) applies to everything, and an extra 0.9% Medicare withholding kicks in on wages above $200,000. State withholding varies.
Why is 22% withholding not enough for most RSU recipients?
Because 22% is a withholding convention, not your tax rate. RSU income stacks on top of salary, and anyone receiving meaningful RSU value is usually in the 24%, 32%, 35%, or 37% bracket. Every vested dollar withheld at 22% but taxed at 35% leaves a 13-cent gap, and on a six-figure vest that adds up to a five-figure April bill.
Are RSUs taxed twice?
No, but sloppy reporting can tax them twice. The vest-date value is taxed once as W-2 wages. When you later sell, only the movement since vest is capital gain or loss. The trap: brokers often report a zero or purchase-price cost basis on Form 1099-B, and if you file that number without adjusting basis to the vest-date value on Form 8949, you pay capital gains tax on income you already paid wage tax on.
What is sell-to-cover and is it enough?
Sell-to-cover means the broker automatically sells enough vested shares to fund the required withholding, and you keep the rest. It covers the withholding, not the tax. Because the withholding itself runs at the flat 22%, sell-to-cover leaves the same shortfall as any other settlement method for anyone above the 24% bracket. Treat it as a down payment.
Can I ask my employer to withhold more than 22% on RSUs?
Some payroll systems allow a higher flat election on supplemental wages or additional withholding via Form W-4, and some do not; ask your stock plan administrator. If your employer cannot increase the RSU withholding itself, the same result comes from adding extra withholding to your regular paychecks (Form W-4, line 4c) or making quarterly estimated payments.
Do I need to make estimated tax payments because of RSUs?
If your total withholding will not reach a safe harbor, yes. The safe harbors: withholding plus timely estimates covering 90% of this year's tax, or 100% of last year's tax (110% if last year's AGI exceeded $150,000). In a big vest year, hitting the prior-year safe harbor is usually the simplest target because that number is already fixed. Miss all the harbors and the IRS charges an underpayment penalty computed quarterly, even if you pay in full by April 15.
How do RSUs affect Social Security and Medicare taxes?
Vested RSU value is FICA wages. Social Security tax stops once total wages reach $184,500 in 2026, so a vest landing after your salary has crossed the base adds no Social Security tax. Medicare has no cap, and employers must withhold an extra 0.9% on wages above $200,000. Married couples can still owe more Additional Medicare Tax at filing because the $250,000 joint threshold is measured on combined wages while each employer only watches its own $200,000 line.
What happens if my RSU shares drop after vesting?
The wage income is locked at the vest-date value; a later decline is a capital loss only when you sell, and capital losses offset capital gains plus at most $3,000 of ordinary income per year. Vest at $80, watch it fall to $50, and you still owe full wage tax on $80. This asymmetry is the standard argument for selling at vest unless you would actively buy the stock at that price with fresh cash.
How are RSUs taxed at vesting vs at sale?
At vesting: the full market value of delivered shares is ordinary W-2 income, at rates up to 37% federal, plus FICA and state tax. At sale: the difference between sale price and vest-date basis is capital gain or loss, long-term if held more than a year after vest. There is no way to convert the vest-date layer into capital gain, and no 83(b) election exists for RSUs.
Does the 37% withholding above $1 million fix the problem for large vests?
Mostly, yes. Once cumulative supplemental wages for the year top $1 million, employers must withhold 37%, the top bracket rate, on the excess. That usually over-withholds slightly. The stubborn gap lives in the wide middle: vests that push total income deep into the 32% and 35% brackets while every supplemental dollar is still withheld at 22%.
Who can help me plan RSU taxes before April?
A CPA who runs a year-end projection with your vest schedule and pay stubs, then sets the withholding change or estimate. Taxstra does this for tech employees in all 50 states as part of a planning engagement.
If I am short, is it better to raise W-4 withholding or send an estimate?
Withholding added late in the year is treated as paid evenly across all four quarters, so it can fix earlier underpayment; an estimate counts only from the date you pay it. For a gap found in the fall, extra withholding is usually the cleaner fix.
Does meeting the safe harbor mean I will not owe in April?
No. The safe harbor (110% of last year's tax when last year's AGI exceeded $150,000, or 90% of this year's tax) prevents the underpayment penalty, not the balance due.
Do states under-withhold RSUs too?
Frequently. Many states use their own flat supplemental rates, which may sit below your actual state marginal rate, and a few withhold nothing by default. High-tax states with progressive brackets, like California, produce the same gap in miniature. If you moved between grant and vest, states also split the income under their sourcing rules, which withholding almost never gets right on its own.
Close the RSU Withholding Gap Before April Finds It
Book a free 30-minute consultation with our team. Tell us what you need, learn how Taxstra can help, and explore whether our services are a good fit. Tax advice, document reviews, and analysis require a paid engagement.Your tax plan and specific advice come after you engage. The call is about fit and next steps.
Tax planning slots are limited before year-end.
Primary sources checked October 20, 2026
An equity decision coming up?
Coordinate vesting, exercises, sales, withholding, and the rest of your return before a deadline drives the decision.
Explore equity-compensation tax planning →