Your vest confirmation shows one withholding rate but you suspect you will owe more — or less — when you file. This guide explains the difference between payroll withholding and annual tax without telling you how to file.
Start here
What you need before using this
- confirmation or pay stub showing amounts.
- Annual salary and bonus expectations.
- Filing status and state of residence.
- Prior-year return if you had a balance due after vests.
Withholding mechanics vary by employer payroll provider. Rates cited follow IRS publications for the reviewed tax year.
Why this happens
Employer is not final tax. IRS Publication 15 describes methods employers may use on equity vests. Those methods aim to collect tax near the time of payment — they do not compute your full annual return.
rates: A common approach withholds a flat federal rate (22% in many situations for income tax under current tables) on the supplemental portion, plus FICA where applicable. If your marginal bracket on combined income is higher, may be lower than your eventual liability.
Salary plus bonus plus : income stacks with other wages in the same calendar year. Your bracket is determined by total taxable income — not by each pay event in isolation.
Payroll taxes: Social Security and Medicare apply to wages up to applicable limits. They are separate from federal income tax and show as distinct lines on your pay stub.
State taxes: Some states mirror federal supplemental methods; others use different tables or have no wage tax. Compare state on your stub to your state's rules — we cite state agency sources on state-specific pages.
: When your employer sells shares to cover , the tax mechanics of the are the same — you received wage income and tax was remitted via . changes cash flow, not whether income is wages.
Estimated payments: If falls short, you may need quarterly estimated payments to reduce underpayment interest. IRS safe-harbor rules are described in Publication 505 — eligibility depends on your prior-year tax.
Filing-season reconciliation: On your return, total wages from (including income) are taxed at your effective rates. Amounts already withheld reduce what you owe at filing — a balance due means plus credits were less than total liability, not that the was taxed twice.
What to check
- Federal rate on confirmation vs your estimated marginal bracket.
- Total Box 1 wages after vs salary alone.
- State line on pay stub after .
- FICA amounts — separate from income tax gap.
- YTD on December pay stub vs expected total tax.
- Whether you made estimated payments or W-4 changes during the year.
Assuming 22% withholding means 22% final tax
What to check in your documents
- confirmation: gross income, rate, shares sold.
- Pay stub: federal, state, and FICA lines for pay period.
- : total wages and total for reconciliation.
- Form 1040 from prior year if you owed after vests.
Example scenario (hypothetical)
Illustration only, not your tax situation.
Questions people ask
- Did my employer withhold too little on purpose?
- Payroll follows tables and supplemental methods — not your full annual return. A gap often means your total income is higher than the rate used on the alone, not that payroll made a mistake.
- Should I change my W-4 after every vest?
- Many people adjust W-4 or make estimated payments when a calculator shows a material gap. The IRS estimator can model scenarios with your pay stubs.
- Does sell-to-cover fix withholding gaps?
- remits tax via withheld shares, but the rate applied may still be the flat supplemental rate. You can still owe at filing if your bracket is higher.
- Where is RSU income on my W-2?
- value is included in Box 1 wages. Some employers add detail in Box 14 or a separate equity tax statement — see our guide for how to read it.
When to get help from a tax pro
- gaps recur every year despite adjustments.
- You have multi-state wages or remote work.
- You also exercised or in the same year.
- You are unsure whether safe-harbor estimated payments apply.
Related calculators
- RSU Withholding Gap Calculator
Focus on the gap between what your employer withholds on RSU vests and what you may owe when everything is reconciled.
- RSU Tax Calculator
Model federal and state taxes on your RSU vest, compare withholding to estimated tax, and see what you may keep.
- RSU Sell-to-Cover Calculator
Model sell-to-cover mechanics. shares sold for withholding, shares delivered net, and cash you may still need.
Related pages
- Why Was My RSU Withholding Only 22%?
Employers commonly use flat supplemental rates on RSU vests. Your actual tax can be higher if you are in a higher bracket.
- RSUs and Estimated Tax Payments
If withholding on a vest falls short, estimated payments may be part of staying on track before April.
- How RSUs Are Taxed
RSUs are usually taxed as wages when they vest, not when the grant is signed. This guide walks through the timeline in plain terms.
Sources and notes
Primary tax claims on this page are supported by the official and secondary sources below. Broker and software links describe reporting mechanics — confirm rules against IRS or state guidance.
Supplemental wage withholding vs annual tax on stacked wage income.
- IRS Publication 15 (Circular E) — Supplemental wages
Internal Revenue Service · Official
Section 7 describes supplemental wage withholding, including the optional 22% flat rate and 37% rate above $1 million of supplemental wages in a calendar year.
- IRS Publication 525 — Taxable and Nontaxable Income
Internal Revenue Service · Official
Covers compensation income from stock-based pay, including restricted property under section 83.
- Filing taxes for restricted stock, RSUs, or performance awards (tax guide PDF)
Fidelity Stock Plan Services · Brokerage explainer
Explains W-2 vest income, 1099-B with $0 basis, supplemental adjusted cost basis, and Form 8949 reporting.
For learning, not filing
VestingTax.com is not a CPA firm or tax preparer. Grants, employers, and states all differ. Use the cited IRS and state sources above, your own documents, and a qualified tax professional before you make decisions from this guide.