Why your W-2 Box 1 is lower than your final paystub
Your last paystub says you made $84,000 but your W-2 says $72,500. Here's the math — and why it's actually a good thing.
Every January, millions of people pull up their final paystub from December, then open their W-2, and notice the numbers don't match. The W-2's Box 1 — what the IRS sees as your wages — is almost always lower than what's printed on your last paystub. It's not a mistake. It's the entire point of contributing to a 401(k) or HSA.
The short answer
Your paystub shows gross pay. Your W-2 Box 1 shows federal taxable wages — which is gross pay minus every pre-tax deduction. The two are almost never equal unless you have zero pre-tax benefits.
The math, line by line
Start with your final paystub's year-to-date gross. Then subtract:
- Traditional 401(k) contributions (reported on W-2 Box 12 with code D)
- Pre-tax HSA contributions through payroll (Box 12W)
- Traditional FSA contributions
- Medical, dental, vision premiums paid pre-tax
- Pre-tax commuter benefits (parking, transit)
- Dependent Care FSA (Box 10)
What's left is your Box 1 wages. If you contributed $10,000 to a 401(k), $4,000 to an HSA, and $2,500 in health premiums on a $84,000 salary, Box 1 lands at $67,500.
Why Box 3 (Social Security wages) is usually higher than Box 1
401(k) and pre-tax health premiums don't reduce Social Security wages — they only reduce federal income tax wages. HSA reduces all three (Box 1, Box 3, Box 5). That's the HSA's unique advantage, and a big reason it's called a triple-tax-advantaged account.
Cross-check your math
Take your final paystub's YTD gross, subtract Box 12 codes D + W + others, subtract pre-tax health premium total, and you should land within $50 of Box 1. If you're way off, contact payroll before filing.
When the gap is a problem
If your W-2 Box 1 is dramatically lower than expected — say, the gap is bigger than the sum of your Box 12 codes — that's worth a call to payroll. Most often it's a missing imputed-income line (group term life insurance over $50,000, employer-provided car, etc.) that wasn't on your paystub but does belong on the W-2. Otherwise, the gap is the entire point of the tax-advantaged accounts working as designed.
Bottom line
A bigger gap between your paystub gross and your W-2 Box 1 usually means you're using pre-tax benefits aggressively — which means you're saving on this year's federal income tax. The W-2 number is the right one for filing.
See it in your own paystub
Upload your PDF and the AI will show how every line plays into the bigger picture.
Affiliate link — we may earn a commission at no cost to you.