US Bonus Tax Calculator (Aggregate vs Supplemental)

Year-End Bonus Tax Guide

Why Your Bonus Feels Heavily Taxed?

When you get a $10,000 bonus and take home only $6,500-7,000, it FEELS like you've been taxed at 30%+. Reality: it's mostly withholding, not actual tax. Federal supplemental withholding rate: 22% on bonuses under $1M cumulative supplemental wages this year. 37% above $1M. PLUS Social Security 6.2% (up to wage base) + Medicare 1.45% + state tax. Total withheld: typically 30-40%. But your ACTUAL tax depends on your marginal rate when filing. If your marginal rate is 24%, you'll get some of the withheld amount refunded when you file, since the flat withholding rate on bonuses is often higher than your actual marginal tax rate on that income.

What's the difference between Supplemental and Aggregate Method?

Two IRS-approved methods for bonus withholding: SUPPLEMENTAL (most common): Flat 22% federal withholding on bonus regardless of your normal income. Simple, predictable. AGGREGATE: Employer adds bonus to your most recent paycheck, calculates withholding as if that's your normal pay rate, then subtracts what they already withheld. Often results in HIGHER withholding for the bonus pay period because that combined check is in a higher bracket. Which is better? Depends on your tax situation. Supplemental method withholding is simpler and more predictable for the employer, which is why most companies default to it regardless of which method might work out better for any individual employee.

What's the key thing to understand about Maximizing Your Bonus Through 401(k)?

If your bonus arrives before you've maxed 401(k) for the year ($23,500 limit 2025, $31,000 if 50+), consider deferring up to 100% into 401(k). Eliminates federal AND state income tax on that portion (FICA still applies). Example: $20,000 bonus, defer $15,000 to 401(k) (and you've already contributed $8,500 from regular paychecks). Tax savings at 32% marginal rate: $4,800. Risk: lose employer match if percentage-based match runs out. Check employer 'true-up' provision — best employers true-up year-end contributions to ensure you still receive the full match even if you front-loaded contributions earlier in the year.

When to Take a Bonus Differently?

Some structures allow bonus optimization: (1) Defer bonus to next tax year if approaching higher bracket or IRMAA cliff this year. (2) Direct a portion to charitable contribution (Donor Advised Fund) for itemized deduction. (3) Use bonus for HSA contribution ($4,300 single / $8,550 family 2025) — pre-tax through payroll. (4) Convert bonus to severance or sign-on bonus tied to multi-year vesting (negotiable for senior roles). (5) Pay deductible items in bonus year — property tax, charitable, medical expenses, and other deductible costs can be timed to fall in the same tax year as a large bonus, helping offset the additional income for tax purposes.