A supplemental check is a follow-up payment that covers the gap between what you were originally paid and what you’re actually owed. In payroll, that means a bonus, commission, retroactive raise, severance, or unused-vacation payout arriving outside your normal pay cycle. In insurance, it means a second payment from your carrier after hidden damage turns up during repairs. The piece most people want to know about a supplemental check is the tax: the IRS lets employers withhold federal income tax at a flat 22% on these payments, which is why a bonus often lands smaller than expected.
What Counts as Supplemental Wages
The IRS defines supplemental wages as any wage payment to an employee that isn’t regular pay. Regular pay is what you earn at your normal hourly, daily, or salaried rate for a standard pay period; anything outside that pattern falls into the supplemental category. Publication 15 lists bonuses, commissions, overtime pay, accumulated sick leave payouts, severance pay, awards, prizes, back pay, retroactive pay increases, and reported tips.1Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide Taxable fringe benefits and expense allowances paid under a nonaccountable plan also count.
Employers have some flexibility at the edges. Overtime pay and tips can be treated as regular wages rather than supplemental if the employer chooses.2eCFR. 26 CFR 31.3402(g)-1 – Supplemental Wage Payments That choice changes how much federal income tax comes out, which matters when you’re planning around a commission-heavy month.
When You’ll See One
Supplemental checks show up whenever compensation doesn’t fit the normal cycle. If your employer approves a raise retroactive to three months ago, the accumulated difference between your old and new rate typically arrives as its own payment. Sales commissions often land separately because the amount changes each period and is easier to process apart from a fixed salary.
Severance pay and payouts for unused vacation time also qualify. When you leave a job and get a lump sum for accrued days, that payment is treated as supplemental wages subject to employment taxes.3Internal Revenue Service. Employer’s Supplemental Tax Guide (2026) Severance works the same way: it feels like a final paycheck, but the IRS treats it as supplemental because it doesn’t correspond to a regular pay period.
Government agencies use the same label in a different setting. The IRS can issue a supplemental payment if a manual review of your return catches an error and the corrected figure means a larger refund.4Internal Revenue Service. Refunds
How Federal Income Tax Is Withheld
Employers use one of two methods to withhold federal income tax on supplemental wages, and which one applies changes your take-home meaningfully.
The Flat 22% Method
When a supplemental payment is issued separately from your regular paycheck, or combined with regular pay but identified as a distinct amount, your employer can withhold a flat 22% for federal income tax.5Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide – Section: Supplemental Wages No other percentage is allowed under this method. Your W-4 entries and filing status don’t factor in. Payroll departments favor it because it’s simple to apply.
The Aggregate Method
If supplemental wages are combined with your regular pay and the employer doesn’t separately identify the supplemental amount, the whole thing is treated as one regular wage payment for that pay period.6Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide – Section: Supplemental Wages Combined With Regular Wages Your employer runs the total through the standard tax tables based on your W-4. Because the tables apply progressive rates to what now looks like an unusually large paycheck, this method often produces a higher effective withholding percentage than the flat 22% approach, especially on mid-to-large payments.
The 37% Rate Above $1 Million
If your supplemental wages from one employer exceed $1 million in a calendar year, every dollar above that threshold is subject to a mandatory flat 37% withholding rate, matching the highest individual income tax bracket.2eCFR. 26 CFR 31.3402(g)-1 – Supplemental Wage Payments The rate applies automatically regardless of your W-4. The first $1 million still follows the 22% flat rate or the aggregate method; only the excess is taxed at 37%.5Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide – Section: Supplemental Wages
Social Security and Medicare Still Apply
The 22% covers federal income tax only. Supplemental wages are also subject to FICA taxes, which your employer withholds separately. For 2026, the employee share is 6.2% for Social Security and 1.45% for Medicare, totaling 7.65%.3Internal Revenue Service. Employer’s Supplemental Tax Guide (2026) The employer matches with another 7.65%.
Social Security tax stops once your total wages for the year reach the wage base, $184,500 for 2026.7Social Security Administration. Contribution and Benefit Base If your regular salary plus supplemental pay pushes you past that cap, no more Social Security tax is withheld on the excess. Medicare has no cap and applies to every dollar.
An Additional Medicare Tax of 0.9% kicks in once your wages cross $200,000 in a calendar year, or $250,000 for married couples filing jointly.8Internal Revenue Service. Topic No. 560, Additional Medicare Tax Your employer starts withholding it after your wages pass $200,000, regardless of filing status. A large supplemental payment that pushes you across that line will pick up the extra 0.9% on the amount above it.
State Withholding on Top
Many states withhold on supplemental wages as well. Some set a flat supplemental rate; others require employers to use the same graduated tables they apply to regular pay. Rates vary widely, from under 2% in some states to over 10% in others, and a handful of states have no income tax at all. Check your state’s tax agency for the exact figure or method.
Why the 22% May Not Match What You Actually Owe
The flat 22% is a payroll convenience, not a match to your real tax rate. Your final liability depends on total income and filing status, not on how withholding was calculated during the year.
For 2026, the 22% bracket runs from $50,400 to $105,700 for single filers and from $100,800 to $211,400 for married couples filing jointly.9Internal Revenue Service. Tax Inflation Adjustments for Tax Year 2026 If your combined regular and supplemental income puts you in the 24%, 32%, or 35% bracket, the 22% withheld from a bonus won’t be enough, and you’ll owe the difference at filing. A large enough shortfall can trigger an underpayment penalty.
The reverse also happens. If your total income sits in the 12% bracket or lower, 22% was too much and the excess comes back as part of your refund. If you’re expecting a large supplemental payment and know you’ll land in a higher bracket, an estimated tax payment or a W-4 adjustment on your remaining regular paychecks can close the gap before April.
Supplemental Checks in Insurance Claims
The same term shows up in property and auto insurance, and it works differently. An insurance claim usually opens with an estimate based on visible damage. Once a contractor removes drywall, roofing, or a damaged vehicle panel, hidden structural or mechanical problems often appear. A supplemental claim covers that gap: instead of paying out of pocket, you keep the claim open and submit a revised estimate from your contractor. If the insurer approves it, a second payment follows to cover the newly documented damage.
Every policy sets a deadline for filing supplemental claims after the date of loss. Windows vary by state and by policy, generally running from roughly 18 months to three years. The conditions section of your policy has the exact figure, and filing after it can mean a full denial regardless of the damage’s legitimacy. Unlike the payroll version, an insurance supplemental check is not wages and is not subject to the 22% withholding rule at all; it’s a claim payment governed by your policy.