HSA vs 401(k): Which Pre-Tax Deduction Keeps More of Your Paycheck?
Quick answer
Dollar for dollar, a payroll HSA contribution keeps more of your paycheck than a traditional 401(k) contribution: the HSA skips federal income tax, most state income taxes, and the 7.65% FICA tax, while 401(k) deferrals skip only the income taxes. For a single $65,000 earner in 2026, maxing the $4,400 self-only HSA saves $1,041 in tax and costs $3,359 of take-home; the same $4,400 into the 401(k) saves $704 and costs $3,696. Order: 401(k) to the full employer match, then the HSA, then more 401(k).
The one difference that decides it: FICA
Both accounts are "pre-tax," but the phrase hides two different tax treatments that matter every payday.
A traditional 401(k), 403(b) or TSP deferral is excluded from federal income tax and, in nearly every state, from state income tax. It is not excluded from Social Security (6.2% up to the 2026 wage base of $184,500) or Medicare (1.45%, plus 0.9% above $200,000 single / $250,000 joint). Look at your W-2: Box 1 (wages for income tax) is lower than Boxes 3 and 5 (Social Security and Medicare wages) by exactly your 401(k) deferral. That gap is the proof.
A payroll HSA contribution made through a Section 125 cafeteria plan is excluded from all three: federal income tax, state income tax in 48 states, and FICA. It comes off Boxes 1, 3 and 5 alike, as do pre-tax health premiums and health FSA contributions run through the same plan.
So for every dollar below the Social Security wage base, the HSA saves your marginal income-tax rate plus 7.65 cents, and the 401(k) saves the income-tax rate alone. That edge holds at every income until you cross $184,500, where it shrinks to the 1.45% (or 2.35%) Medicare rate.
The 2026 limits from the IRS: HSA $4,400 self-only, $8,750 family, plus a $1,000 catch-up from age 55. 401(k) elective deferral $24,500, plus an $8,000 catch-up from age 50 and $11,250 at ages 60 to 63 under SECURE 2.0.
Worked example: $4,400 into each account
Use the Take-Home Pay Calculator default earner: $65,000 salary, single, paid biweekly, 5% traditional 401(k) ($3,250), $2,400 in pre-tax health premiums, no HSA, 4% state effective rate. Baseline take-home is $47,245 a year ($1,817 per check). Taxable income is $43,250, which sits in the 12% bracket with $7,150 of room, so every extra pre-tax dollar in this example is worth 12% federal plus 4% state.
Option A: max the HSA through payroll, $4,400.
- Federal income tax saved: 12% x $4,400 = $528
- State tax saved: 4% x $4,400 = $176
- Social Security saved: 6.2% x $4,400 = $273
- Medicare saved: 1.45% x $4,400 = $64
- Total tax saved: $1,041. Take-home falls by $3,359 ($129 per check) and $4,400 lands in the HSA.
Option B: put an extra $4,400 into the traditional 401(k) (raising the contribution from 5% to about 11.8% of pay).
- Federal income tax saved: $528
- State tax saved: $176
- FICA saved: $0
- Total tax saved: $704. Take-home falls by $3,696 ($142 per check) and $4,400 lands in the 401(k).
Same $4,400 saved, same investment growth available, and Option A leaves $337 more in your checking account over the year. That $337 is exactly 7.65% of $4,400, and it recurs every year you contribute; invested at 6% for 30 years the FICA gap alone grows to more than $26,000, before counting the HSA's tax-free medical withdrawals.
Tax saved per $1,000 at each 2026 bracket
The FICA edge is a constant $76.50 per $1,000 below the wage base, so the HSA wins by the same dollar margin in the 12% and 24% brackets; the percentage advantage is largest for lower earners. Figures assume a 4% state rate and single filing; no-tax-state earners subtract $40 from every cell.
| Federal bracket (2026 single taxable income) | HSA via payroll saves | Traditional 401(k) saves | HSA edge |
|---|---|---|---|
| 12% ($12,401 to $50,400) | $236.50 | $160.00 | $76.50 |
| 22% ($50,401 to $105,700) | $336.50 | $260.00 | $76.50 |
| 24% ($105,701 to $201,775) | $356.50 | $280.00 | $76.50 |
| 24%, wages above $184,500 SS base | $294.50 | $280.00 | $14.50 |
| 32% ($201,776 to $256,225), above $200k Medicare line | $383.50 | $360.00 | $23.50 |
Two things to notice. First, the HSA's edge nearly disappears once wages pass the Social Security wage base, so a $220,000 earner should think of the two accounts as roughly equal on the way in and choose based on what the money is for. Second, an HSA contribution made outside payroll (writing a check to the HSA custodian and deducting it on Form 8889) gets the income-tax deduction but not the FICA exclusion. If your employer offers payroll HSA deduction, always use it. The Tax Bracket Explainer shows which row you are in for 2026.
When the 401(k) should still come first
The employer match changes the order. If your employer matches 50% of contributions up to 6% of pay, every dollar you defer up to that 6% earns an immediate 50-cent match. No tax treatment beats a 50% (or 100%) instant return. On the $65,000 example, contributing 6% instead of 5% costs $546 of take-home, saves $104 in tax, and adds a $325 match at 50%, so the account gains $975 for $546 of spendable money.
The correct sequence for most people with an HSA-eligible plan is therefore:
- Traditional or Roth 401(k) up to the full employer match.
- HSA to the annual limit ($4,400 self / $8,750 family, +$1,000 at 55+), through payroll.
- Additional 401(k) deferrals toward the $24,500 limit, or a Roth IRA ($7,500 in 2026) if you expect a higher bracket in retirement.
Run your own match percentages in the 401(k) Employer Match Calculator to find exactly where step 1 ends; then run your own numbers in the Take-Home Pay Calculator, which builds a ranked Lever Board that shows the tax saved and take-home cost of the HSA and 401(k) moves side by side for your salary and state.
Three HSA caveats the paycheck math does not show
You need an HSA-eligible high-deductible health plan. If your employer's HDHP carries a much higher deductible than the PPO alternative and you have predictable medical costs, the premium and deductible difference can swamp the $337-a-year FICA edge. Compare total expected cost (premiums + expected out-of-pocket - tax saved), not just the tax saving.
California and New Jersey do not recognize HSAs. Both tax HSA contributions and earnings as ordinary income at the state level. A California earner still saves 7.65% FICA and the federal rate on payroll HSA dollars, but not the state portion, so the HSA's edge per $1,000 falls from $76.50 to $76.50 minus the state rate (about $36.50 at a 4% rate). The 401(k) stays fully state-deductible in both states.
HSA money is for medical costs until 65. Non-medical withdrawals before 65 are taxed as income plus a 20% penalty (versus 10% for 401(k) withdrawals before 59 1/2). After 65, HSA withdrawals for anything are taxed like a traditional IRA with no penalty, and medical withdrawals stay tax-free at any age. Because you can reimburse yourself years later for receipts you kept, the best play is to pay current medical bills from cash, invest the HSA, and save the receipts. The HSA Maximizer models that long-hold strategy.
One small cost of skipping FICA: HSA contributions reduce your Social Security wages, so they trim the earnings record that sets your future benefit by a few dollars a month for a mid-career earner, far less than the $273 a year saved in Social Security tax.
Pre-tax 401(k) vs Roth 401(k) in the same paycheck
A Roth 401(k) deferral is taken after income tax and after FICA, so it reduces take-home by the full contribution. On the $65,000 example, the 5% ($3,250) contribution costs $3,250 of take-home as Roth versus $2,730 as traditional, a $520 difference ($20 per biweekly check), because the traditional version saves 12% federal and 4% state today. The Roth's payoff is tax-free growth at withdrawal, usually worth that $520 in the 12% bracket and harder to justify from the 24% bracket up. Either way, the HSA is the only one of the three that skips FICA.
FAQ
Q: Does an HSA contribution reduce Social Security and Medicare tax?
Yes, if it is made through your employer's Section 125 cafeteria plan via payroll. Those contributions are excluded from Social Security wages (Box 3) and Medicare wages (Box 5) on your W-2, saving 7.65% below the $184,500 wage base. Contributions you make directly to the HSA custodian and deduct on Form 8889 save income tax only.
Q: Does a 401(k) contribution reduce FICA tax?
No. Traditional 401(k), 403(b), and TSP elective deferrals are subject to the 6.2% Social Security and 1.45% Medicare taxes. They are excluded from federal income tax and from state income tax in most states, which is why a $1,000 deferral in the 22% bracket with a 4% state rate saves $260 rather than the $336.50 a payroll HSA contribution saves.
Q: Which should I max first, the HSA or the 401(k)?
Contribute to the 401(k) up to the full employer match first, because a 50% or 100% match beats any tax exclusion. Then max the HSA ($4,400 self-only or $8,750 family in 2026, plus $1,000 at age 55 and up). Then return to the 401(k) toward its $24,500 limit. If you have no match, start with the HSA.
Q: How much take-home does a $4,400 HSA contribution cost per paycheck?
About $129 per biweekly paycheck for a single earner in the 12% bracket with a 4% state rate ($3,359 a year), and about $112 per check ($2,919 a year) in the 22% bracket. The same $4,400 into a traditional 401(k) costs $142 per check in the 12% bracket and $125 in the 22% bracket, because FICA is still charged on 401(k) deferrals.
Q: Is the HSA still better if I am over the Social Security wage base?
Only slightly on the way in. Above $184,500 of wages the 6.2% Social Security tax has already stopped, so the payroll HSA's edge over a 401(k) shrinks to the 1.45% Medicare rate, or 2.35% above $200,000 single. At that income the decision rests on the HSA's tax-free medical withdrawals versus the 401(k)'s higher limit and any employer match.