What Is the RSU Tax Withholding Gap and How Do You Close It?
Last reviewed: July 2026
The RSU tax withholding gap is the difference between the flat 22% your employer withholds when your restricted stock units vest and the 32%, 35%, or 37% you actually owe at your real federal bracket. That gap does not disappear. It sits on every vest and grows until April, when it lands as a bill your CPA cannot undo. For the engineers, product managers, and biotech staff we work with around Forest Hill and across the Baltimore metro, it is the most consistent equity-compensation mistake I see, and it is structural, not a math error you made.
Key Takeaways
- The RSU tax withholding gap is the spread between the flat 22% supplemental rate your employer withholds and your real 32% to 37% bracket.
- For 2026, the top federal rate is 37% on income above $640,600 single or $768,700 married filing jointly, far above the 22% withheld.
- You generally owe quarterly estimated tax once the gap pushes you past $1,000 owed; the penalty is the federal short-term rate plus 3 points.
- Maryland adds a state income tax up to 5.75% on every vested share, on top of the federal gap, for Harford County residents.
About the Author: Jeff Judge, CFP®, AEP®, ChFC®, CLU® is Managing Partner of Chesapeake Financial Planners in Forest Hill, Maryland. He has been helping families and business owners in Harford County and the Baltimore metro area navigate equity compensation and tax planning since earning his CFP® certification in 2013, by using Chesapeake's signature process, the R.U.D.D.E.R. Method™. "The clients who get burned are not careless," Jeff says. "They are smart, well-paid people who assumed the company handled the tax, and nobody showed them the gap until the bill arrived."
How Does the RSU Tax Withholding Gap Actually Happen?
The RSU tax withholding gap happens because the rate your employer uses to withhold has nothing to do with the rate you actually pay. When your restricted stock units vest, the shares delivered to you are ordinary income that year. The value on vesting day times the number of shares lands on your W-2 as wages, and you owe ordinary income tax on the full amount whether you sell a single share or not.
The company covers the tax by holding back shares at vest. The trouble is the rate. RSU income is supplemental wages, and the IRS sets a flat default. According to IRS Publication 15, the rate is 22% on supplemental wages up to $1 million in a year, then 37% above $1 million. The 22% is a payroll convenience that has held since 2018, unrelated to your marginal bracket. If your salary and vesting push you into the 35% bracket, you are short by 13 points on every dollar that vested, and that shortfall stays invisible until it surfaces in March.
How Much Is the Gap in Real Dollars?
In dollar terms, the federal gap on a single large vest can run past $15,000 before any state tax, and it compounds across a multi-year schedule. The numbers below are a hypothetical illustration, not a promise or a quote of your result. Picture a tech employee with $350,000 of total compensation who vests $100,000 of RSUs in a year. The employer withholds 22%, or $22,000, but the marginal federal rate on that income is 37%, so the correct withholding would be $37,000. The federal gap is $15,000, before the state takes its cut:
| Line item | Rate | Amount on a $100,000 vest |
|---|---|---|
| Employer withheld (supplemental) | 22% | $22,000 |
| Federal actually owed (top bracket) | 37% | $37,000 |
| Federal gap | 15 points | $15,000 |
| Maryland state tax (top rate) | up to 5.75% | up to $5,750 |
| Combined federal plus Maryland gap | blended | roughly $20,750 |
Now multiply that across a vest schedule. A four-year grant with six-figure vesting years builds a shortfall in the tens of thousands if you make no adjustments. The people hit hardest are the ones with the largest vesting years who assumed the company had it covered.
Why Won't Your Company Just Fix the Withholding?
Your company will not fix it because the 22% supplemental rate is the IRS-permitted default, and your employer is following the rule, not making an error. An alternative exists, the aggregate method, where the company combines your RSU income with your regular wages and withholds as if it all arrived in one paycheck, landing closer to your real rate. Most companies do not offer it. The tax liability is yours; the withholding is the company's best administrative approximation. Those two numbers do not have to match, and in a high-bracket year, they will not.
Can you ask payroll to withhold more on your RSUs? Sometimes, yes. Some employers let you elect a higher supplemental rate for RSU vests, and it is worth asking equity plan administration whether yours does. But even at 25% or 30%, you are still short if your effective rate is 37%. The dependable fix is adjusting what you control outside the company.
"Your company is not your tax planner. The 22% is a payroll setting, not a calculation of what you owe, and assuming those two are the same is the single most expensive equity mistake I watch high earners make." (Jeff Judge, CFP®)
How Do You Close the Gap With Estimated Taxes and a Written Plan?
You close the gap by paying quarterly estimated tax directly to the IRS and to Maryland for the shortfall each vest creates. The IRS expects tax paid as income is earned. According to the IRS, you generally must make estimated payments once you expect to owe $1,000 or more at filing, or you face an underpayment penalty.
Safe-harbor rules tell you how much is enough to avoid that penalty: cover at least 90% of your current-year tax or 100% of your prior-year tax. For higher earners the prior-year figure is 110%; the IRS applies that 110% threshold when your prior-year adjusted gross income was above $150,000, which fits most people with meaningful RSU income. The penalty itself, per the IRS quarterly interest rates page, is the "Federal short-term rate plus 3 percentage points," compounded daily. The 2026 federal estimated deadlines fall on April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027.
The piece most people skip is not knowing estimated taxes exist. It is that the right amount needs your actual bracket, the net income from the vest, and your full projected income in one view. A written equity plan answers that for every grant before each event: the tax and estimated payment schedule per vest; the sell strategy, including the alternative minimum tax math on incentive stock options and the qualifying versus disqualifying disposition timeline; how a high-vest year interacts with a Roth conversion, a 401(k) catch-up, or donor-advised-fund giving; and the 90-day window to exercise ISOs after you leave before they expire.
This is where our R.U.D.D.E.R. Method™ earns its keep. The R.U.D.D.E.R. Method™ is Chesapeake Financial Planners' six-step planning process: Review and Recognize, Uncover and Understand, Design and Develop, Discuss and Decide, Execute and Empower, and Reassess and Refine. Review maps your vesting calendar in January, Uncover calculates the exact gap across federal and Maryland tax, and Design turns it into a W-4 change and estimated payment schedule. The plan matters most in three moments: a high-vest year when grants stack, a job change that shifts income while withholding lags, and a layoff with ISOs, where the 90-day clock, the cash to exercise, and the AMT exposure hit at once.
How does the gap relate to concentrated employer-stock risk? The withholding gap is a cash flow problem; concentration is a portfolio problem, and they run in parallel. When a large slice of your net worth sits in your employer's stock, you depend on one company for your salary, your benefits, and your vesting at once. As general education and not a recommendation on any specific security, the common approach is to sell vested shares on a set schedule and redeploy into a diversified mix, so the decision is deliberate rather than driven by the urge to keep holding a stock that has run up. The people who handle equity well diversified on a plan, consistently.
How Do You Close the Gap Before Next April?
Close the gap with three moves, in order of how fast they help. First, calculate the shortfall on every upcoming vest: gross up your expected income, apply your actual marginal rate, subtract the 22% withheld, and pay an estimated payment for that amount in the quarter the vest occurs. Second, adjust your W-4 to withhold extra federal and state tax each paycheck; it will not cover the whole gap, but it lowers the quarterly burden and is a lever most employees never touch. Third, build a vest-by-vest schedule for the next twelve months, so a high-vest year is something you see in January, not February.
For a deeper walkthrough, see Are RSU Vesting Taxes Higher Than What Your Employer Withholds? and Why isn't my 22% RSU withholding enough, and what will I owe?. If you also hold options or an ESPP, RSU vs ISO vs NSO vs ESPP lays out how each is taxed. Consult a tax professional for your filing.
The gap does not fix itself. It compounds, because the shortfall from earlier years was never addressed and each new vest adds to the pile. I talk to people in Bel Air and across Harford County who have seen four or five vest events and paid a surprise April bill every time without connecting it to a structural problem with a structural fix. That is not a knowledge problem. It is a planning problem, and the RSU tax withholding gap closes the moment someone builds the picture before the bill arrives instead of after.
Frequently Asked Questions
Why does my employer only withhold 22% on my RSUs?
Your employer withholds 22% because the IRS sets that flat default for supplemental wages up to $1 million per year, and RSU income counts as supplemental wages. It is a payroll convenience, not a calculation of your bracket, so high earners in the 32% to 37% brackets are left short on every vested dollar.
How big is the RSU tax withholding gap for a high earner?
The gap is the difference between your real marginal rate and the 22% withheld, multiplied by your vesting income. A person in the 37% bracket with a $100,000 vest faces a $15,000 federal gap before state tax, and Maryland's top 5.75% rate can add several thousand more. The exact figure depends on your total income and filing status.
What are the 2026 quarterly estimated tax deadlines?
For the 2026 tax year, federal estimated tax payments are due April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027. If a date lands on a weekend or holiday, the IRS moves it to the next business day. You generally pay estimated tax once you expect to owe $1,000 or more at filing.
What is the safe harbor that avoids the underpayment penalty?
The safe harbor protects you from the underpayment penalty if your payments cover at least 90% of your current-year tax or 100% of your prior-year tax. If your prior-year adjusted gross income was above $150,000, that prior-year figure rises to 110%. Hitting either threshold shields you even when a large vesting year leaves a balance due.
Does selling my RSUs at vesting reduce the tax I owe?
No, selling at vesting does not reduce the ordinary income tax on the vested value, because that tax is locked in the moment shares vest. Selling immediately does avoid extra capital gains complications and trims single-stock concentration, as general education rather than a recommendation on a specific holding. The proceeds can then fund your estimated payments.
Do I owe Maryland tax on RSU vesting in Harford County?
Yes, RSU vesting income is subject to Maryland state income tax up to 5.75%, plus the Harford County local income tax for residents, on top of the federal gap. Employers often underwithhold at the state level too, using a flat rate that ignores the combined state-and-county burden a Bel Air or Forest Hill resident actually owes.
What happens to my ISOs if I get laid off?
If you hold incentive stock options and leave the company, you generally have a 90-day window to exercise before they expire, regardless of how you left. A layoff makes this acute because the clock starts immediately, exercising costs cash, and exercising and holding can trigger alternative minimum tax. Consult a tax professional and map the decision before notice.
Ready to Close Your RSU Tax Withholding Gap?
If your RSUs are vesting and April still surprises you, the surprise is the symptom and the RSU tax withholding gap is the problem. Jeff Judge and the Chesapeake team serve tech and equity-comp employees across Harford County and the Baltimore metro from our Forest Hill office. Schedule a free fit call at chesapeakefp.com and we will build the vest-by-vest picture before the next bill arrives.
A version of this article was originally published on Jeff Judge's LinkedIn.
Want to go deeper? Our Tech Equity Tax Traps Guide walks through this step by step.
Disclosures
The information provided is for educational purposes only and should not be construed as investment advice. Investment strategies should be tailored to individual circumstances, risk tolerance, and goals. Past performance doesn't guarantee future results. Consult with qualified financial professionals regarding your specific situation.
This information is not intended to be a substitute for specific individualized tax, investment or legal advice. We suggest that you discuss your specific situation with a qualified tax, legal or financial advisor.
Advisors associated with Chesapeake Financial Planners may be either (1) LPL Financial Registered Representatives offering securities through LPL Financial, Member FINRA and SIPC, and investment advisor representatives offering investment advice through Great Valley Advisor Group; or (2) solely investment advisor representatives offering investment advice through Great Valley Advisor Group and not affiliated with LPL Financial. Great Valley Advisor Group, and Chesapeake Financial Planners are separate entities from LPL Financial.
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