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Assumptions and limits2026 tax year · checked Oct 24, 2026

Figures used

Federal withholding on vests
22% (37% over $1,000,000)
Social Security wage base
$184,500
Additional Medicare withheld above
$200,000
California supplemental rate
10.23%
New York supplemental rate
11.7%
Safe harbor
90% this year, or 100% / 110% of last year

Assumed

  • One employer: Social Security and Additional Medicare are withheld as if this job were your only one.
  • Vests that already happened this year are valued at today’s price.
  • Future years use this year’s tax brackets and limits.
  • The ESPP discount is ordinary income in the year you buy, at the discount on the purchase price; nothing is withheld on it.
  • Offers use your filing status, no pre-tax 401(k), and notional shares that move with your price scenario.
  • Sign-on paybacks are prorated by the months left in the payback window.

Not modeled

  • Moving states between grant and vest (California and New York split vests by workdays).
  • Selling shares: capital gains, the cost basis brokers often report as $0, and Form 8949.
  • ESPP lookback, the $25,000 yearly limit and qualifying sales.
  • Stock options, private-company equity and RSUs that settle at an exit.
  • Other income, itemized deductions and credits.

Sources

How we calculate thisReport a problem with this calculation

What the planner does

Every vest, priced and taxed

Enter grants by ticker and share count, or as a dollar value. Each vest is priced at today’s share price moved by your scenario, then withheld the way payroll does: 22% federal, your state’s rate, Social Security and Medicare, with shares sold to cover.

Withheld against owed

The year’s real tax on all your pay, set against what paychecks and vests withheld. The gap comes with estimated payment dates, the safe-harbor amount and the extra withholding per paycheck that would close it.

Years and offers

Pay by year as grants stack and run out, with the years pay falls flagged. Offers sit beside staying after tax, with what leaving after a year or two leaves behind and pays back.

Questions people ask

Why do I owe tax on my RSUs in April?

Employers withhold federal tax on a vest at a flat 22%, whatever your bracket. In 2026, single filers pay 24% above $105,700 of taxable income, 32% above $201,775 and 35% above $256,225, so each vest can leave 10 to 13 cents on the dollar unpaid. The planner adds it up for the year.

Are RSUs taxed twice?

No. A vest is taxed as wages at its market value that day, and that value becomes your cost basis. When you sell, only the gain or loss since the vest is taxed. Brokers often report a $0 basis on Form 1099-B; use the vest value on Form 8949 so you don’t pay tax on it again.

How do I avoid an underpayment penalty?

Pay at least 90% of this year’s tax, or 100% of last year’s (110% if last year’s AGI was over $150,000), through withholding and estimated payments. Withholding counts as paid evenly through the year, so extra withholding late in the year can cover earlier quarters.

Do RSUs count toward the Social Security limit?

Yes. Vests are wages, so Social Security stops once your pay for the year reaches $184,500. Medicare has no cap, and 0.9% more is withheld above $200,000.

Which offer is worth more?

Compare them after tax and year by year. Vesting shapes differ (5/15/40/40 pays little in year one, 40/30/20/10 front-loads), sign-on bonuses often have to be paid back if you leave early, and a job in a state with income tax keeps less of the same pay.

Is what I type saved?

The sample saves nothing. Your own numbers are kept in this browser under your account and cleared when you sign out.