{
  "slug": "rsu-vest-withholding-gap",
  "title": "RSU Vest Tax Withholding Gap Calculator",
  "heading": "RSU Withholding Shortfall Calculator",
  "category": "financial",
  "url": "https://www.revenuelab.fyi/toolbox/rsu-vest-withholding-gap",
  "summary": "Find out if your employer withheld enough tax when your RSUs vested.",
  "description": "Most employers withhold federal tax on RSU vesting at the flat supplemental wage rate of 22% (37% above $1 million in supplemental wages in a year), plus Social Security, Medicare, and state tax. If your actual marginal tax bracket is higher than 22% — which is common once RSU income stacks on top of base salary — the withholding falls short, and you'll owe the difference at tax time, often with an unpleasant surprise and possibly an underpayment penalty. This calculator compares what was actually withheld against what you'll actually owe at your real marginal rate, so you can set aside the shortfall or adjust your W-4 and estimated payments before the bill arrives in April.",
  "formula": "Tax owed = vest value × marginal rate. Tax withheld = vest value × supplemental withholding rate. Shortfall = tax owed − tax withheld (can be negative if over-withheld).",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=rsu-vest-withholding-gap",
  "inputs": [
    {
      "id": "vestValue",
      "label": "Total RSU value vesting this year",
      "kind": "number",
      "hint": null,
      "default": 60000,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "supplementalRate",
      "label": "Employer's supplemental withholding rate",
      "kind": "number",
      "hint": null,
      "default": 22,
      "unit": "%",
      "min": 0,
      "max": 40
    },
    {
      "id": "marginalRate",
      "label": "Your actual federal marginal rate",
      "kind": "number",
      "hint": null,
      "default": 32,
      "unit": "%",
      "min": 0,
      "max": 50
    },
    {
      "id": "stateRate",
      "label": "State tax rate on the vest",
      "kind": "number",
      "hint": null,
      "default": 6,
      "unit": "%",
      "min": 0,
      "max": 15
    },
    {
      "id": "stateWithheld",
      "label": "State withholding rate applied",
      "kind": "number",
      "hint": null,
      "default": 6,
      "unit": "%",
      "min": 0,
      "max": 15
    }
  ],
  "outputs": [
    {
      "id": "totalShortfall",
      "label": "Total tax you still owe (or refund if negative)",
      "format": "currency",
      "hint": null,
      "primary": true
    },
    {
      "id": "fedShortfall",
      "label": "Federal shortfall",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "stateShortfall",
      "label": "State shortfall",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "fedWithheld",
      "label": "Federal tax actually withheld",
      "format": "currency",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Total RSU value vesting this year: 60000 $",
      "Employer's supplemental withholding rate: 22 %",
      "Your actual federal marginal rate: 32 %",
      "State tax rate on the vest: 6 %",
      "State withholding rate applied: 6 %"
    ],
    "outputs": [
      "Total tax you still owe (or refund if negative): $6,000",
      "Federal shortfall: $6,000",
      "State shortfall: $0",
      "Federal tax actually withheld: $13,200"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter total rsu value vesting this year ($).",
      "Enter employer's supplemental withholding rate (%).",
      "Enter your actual federal marginal rate (%).",
      "Enter state tax rate on the vest (%).",
      "Enter state withholding rate applied (%).",
      "Read your total tax you still owe (or refund if negative) on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "vestValue": 36000,
        "supplementalRate": 13,
        "marginalRate": 19,
        "stateRate": 3.5999999999999996,
        "stateWithheld": 3.5999999999999996
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "vestValue": 60000,
        "supplementalRate": 22,
        "marginalRate": 32,
        "stateRate": 6,
        "stateWithheld": 6
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "vestValue": 96000,
        "supplementalRate": 35,
        "marginalRate": 50,
        "stateRate": 9.600000000000001,
        "stateWithheld": 9.600000000000001
      }
    }
  ],
  "limitations": [
    "Results are estimates before tax, fees, and inflation unless an input explicitly covers them.",
    "Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.",
    "This is educational maths, not financial advice. Check anything contractual with the lender or your accountant."
  ],
  "faq": [
    {
      "q": "Why is RSU withholding almost always too low for higher earners?",
      "a": "The IRS default supplemental wage withholding rate is a flat 22% up to $1 million of supplemental income in the year, regardless of your actual bracket. If your combined salary and RSU income puts you in the 32%, 35%, or 37% bracket, that flat 22% withholding on the RSU chunk leaves a real gap that compounds every vest date."
    },
    {
      "q": "How do I avoid an underpayment penalty from this gap?",
      "a": "Either make estimated quarterly tax payments to cover the shortfall, or increase withholding elsewhere — many people add extra flat-dollar withholding on their regular paycheck via Form W-4 to cover the gap without having to manage separate quarterly payments."
    },
    {
      "q": "Does the same withholding issue apply to bonuses?",
      "a": "Yes, bonuses are also 'supplemental wages' under IRS rules and get the same flat 22% federal withholding treatment (or 37% above the $1 million supplemental threshold in a year), so the same shortfall math applies."
    },
    {
      "q": "Can I ask my employer to withhold more than 22% on RSUs?",
      "a": "Most payroll systems apply the flat supplemental rate automatically and don't offer an easy per-vest override, though some allow you to elect additional withholding on your regular paycheck. Check with payroll/HR — a few employers do allow supplemental withholding elections above the statutory minimum."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/espp-discount-return",
    "https://www.revenuelab.fyi/toolbox/amt-iso-exercise",
    "https://www.revenuelab.fyi/toolbox/nqdc-deferred-comp-payout"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — RSU Vest Tax Withholding Gap Calculator (https://www.revenuelab.fyi/toolbox/rsu-vest-withholding-gap)"
}