RSU Tax Calculator: How Much You Actually Owe at Vest in 2026
The under-withholding gap on RSU vests is the most common cause of surprise April 15 tax bills among tech and finance employees.
When Restricted Stock Units (RSUs) vest, the fair market value (FMV) of the shares is added to your W-2 wages and taxed as ordinary income. Federal, FICA (Social Security + Medicare), and state tax all apply at vest. After vest, the shares are treated like any other stock — capital gains tax applies to subsequent appreciation.
The most common mistake high earners make: relying on the 22% IRS default supplemental withholding to cover their RSU tax. For employees in the 32%, 35%, or 37% federal brackets, that creates a 10–15% under-withholding gap, often resulting in unexpected five- or six-figure April 15 bills.
RSU taxation in 2026
Interactive calculator
Estimates only. Consult a licensed CPA or fee-only fiduciary for advice specific to your situation.
The 22% default supplemental withholding under-withholds for high earners. Consider asking your employer to withhold at a higher rate or making quarterly estimated payments to avoid penalties.
How to close the under-withholding gap
Three options. First: ask your employer's payroll team to withhold federal at a higher rate. Some companies allow individual employees to elect a higher withholding rate on RSU vests; many do not.
Second: make quarterly estimated-tax payments to the IRS and your state. Federal estimated payments are due Apr 15, Jun 15, Sep 15, Jan 15 of the following year. Calculate your expected total tax and pay quarters that bring you within safe harbor (90% of current-year liability or 110% of prior-year for high earners).
Third: increase W-4 withholding from your salary. The W-4 lets you specify additional withholding per paycheck; add an amount that covers the RSU shortfall divided across paychecks.
Why selling-at-vest is usually right
When RSUs vest, the FMV is added to your taxable income. You're already taxed on the full vest value as ordinary income. From the moment you receive the shares, your cost basis equals the vest-day FMV. There's no inherent tax advantage to holding — capital gains accrue only on POST-vest appreciation.
Holding past vest is therefore a pure asset-allocation decision: do you want to hold 50% of your net worth in single-employer stock? For most tech employees the answer is no. The selling-at-vest default avoids concentration risk, captures liquidity, and lets you redeploy into a diversified portfolio.
There are exceptions: if you genuinely believe your employer is undervalued AND you can absorb the volatility AND you have substantial diversified holdings outside the equity-comp position, holding is defensible. Otherwise, sell at vest and reinvest in a broad index.
Real-world scenarios
Marcus has $300K base + $500K RSU vest in 2026. CA state rate 13.3%. Employer 'sells to cover' at the 22% default federal rate.
Federal marginal rate: 35%. True federal tax on $500K vest: ~$175K. Default withholding at 22% covers only $110K. Underpayment: $65K federal + $66K CA state. Total April 15 owed: $130K+ if no quarterly estimates were paid.
Sarah's first major vest is $80K on top of a $140K base salary. She had no quarterly estimated payments. MA state rate 5%.
Combined income $220K, putting her in 24% federal bracket. True federal tax on $80K: ~$19K. Default withholding $17.6K. State tax owed: $4K. Manageable shortfall (~$5–6K). Manageable but still warrants a Q3 or Q4 estimated payment to avoid underpayment penalties.
Priya works at a private company. Her RSUs have a double-trigger: vest only after BOTH (1) time-based vesting and (2) liquidity event (IPO or acquisition). She holds 50K shares granted at $5/share.
If the company IPOs at $30, all 50K vested-but-deferred shares trigger as W-2 income on the IPO date: $1.5M of ordinary income. Federal tax could be $500K+. Pre-IPO planning is critical: 10b5-1 plan setup, liquidity for the tax bill, and consideration of secondary-tender exits if available.
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Frequently asked
RSUs vest into shares automatically — no exercise required, no purchase. Stock options must be exercised (purchased at the strike price) before they become shares. RSUs are taxed at vest; ISOs are taxed at exercise (potentially) and at sale; NSOs are taxed at exercise. Different tax planning playbooks for each.
No. Section 83(b) elections apply to property received subject to a substantial risk of forfeiture — typically Restricted Stock Awards (RSAs), where shares are issued upfront with vesting restrictions. RSUs are unfunded promises to deliver shares later, so 83(b) doesn't apply.
Default to sell at vest unless you have a specific reason to hold. Concentration risk in a single employer is the largest avoidable financial-planning mistake at tech firms. Holding for capital-gains treatment doesn't help — your basis is already FMV at vest, so any subsequent gain (the only thing taxed as LTCG) requires waiting an additional year for the lower rate.
Vesting taxes the income in the state where you LIVE on the vest date. If you vested $200K in California then moved to Texas, that $200K is fully CA-source. Subsequent capital gains on those shares (sold post-move) are sourced to Texas. Plan vesting timing if a move is planned.
Federal law mandates 37% supplemental withholding on cumulative supplemental wages exceeding $1M in a calendar year for a single employee. This catches very high RSU vests but most workers stay below the threshold.
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