The key insight most people miss
Contributing to a traditional 401(k) reduces your take-home pay — but by less than the contribution amount. That's because pre-tax 401(k) contributions lower your taxable income, which cuts your federal (and often state) income tax bill at the same time.
In other words, part of every 401(k) dollar you contribute comes back to you as tax savings. The government is effectively subsidising your retirement savings at your marginal tax rate.
Real example: 6% contribution on $75,000
Here's exactly what happens to your paycheck when you contribute 6% to a traditional 401(k) on a $75,000 salary as a single filer.
You put in $4,500 toward retirement but your take-home only drops by $3,510 — because the IRS hands back $990 in tax savings. That's a 22% discount on your retirement savings, just from the tax benefit.
Per bi-weekly paycheck, contributing 6% costs you just $135 less per paycheck while putting $173 into your retirement account every two weeks.
$75,000 salary — all contribution rates
Single filer, no state tax, 2026 federal brackets.
| Rate | Annual contrib. | Fed tax saved | Real cost | Take-home/yr | Per paycheck |
|---|---|---|---|---|---|
| 0% | $0 | — | — | $61,537 | $2,367 |
| 3% | $2,250 | $495 | $1,755 | $59,782 | $2,299 |
| 6% | $4,500 | $990 | $3,510 | $58,027 | $2,232 |
| 10% | $7,500 | $1,650 | $5,850 | $55,687 | $2,142 |
| 15% | $11,250 | $2,256 | $8,994 | $52,543 | $2,021 |
$100,000 salary — the 22% bracket advantage
At $100,000, you're in the 22% federal bracket. The tax savings on each 401(k) dollar are nearly double what they are at $75K.
| Rate | Annual contrib. | Fed tax saved | Real cost | Take-home/yr |
|---|---|---|---|---|
| 0% | $0 | — | — | $79,124 |
| 3% | $3,000 | $660 | $2,340 | $76,784 |
| 6% | $6,000 | $1,320 | $4,680 | $74,444 |
| 10% | $10,000 | $2,200 | $7,800 | $71,324 |
| 15% | $15,000 | $3,300 | $11,700 | $67,424 |
At $100K, contributing 6% ($6,000) only reduces take-home by $4,680 — because $1,320 comes back as federal tax savings. You're getting a 22% discount on every retirement dollar.
2026 contribution limits
To max out a 401(k) at $24,500 on a $75,000 salary, you'd need to contribute 32.7% of your gross — which would bring take-home to roughly $42,000/year. Most financial advisors suggest 10–15% as a realistic target for most workers.
Traditional 401(k) vs Roth 401(k)
This article covers traditional (pre-tax) 401(k) contributions, which reduce your taxable income today. A Roth 401(k) works the opposite way — contributions come from after-tax dollars (no immediate tax saving), but withdrawals in retirement are tax-free.
| Traditional 401(k) | Roth 401(k) | |
|---|---|---|
| Contributions | Pre-tax (reduces taxable income now) | After-tax (no immediate benefit) |
| Effect on paycheck | Take-home drops less than contribution | Take-home drops by full contribution |
| Tax on withdrawals | Taxed as ordinary income in retirement | Tax-free in retirement |
| Best for | Higher earners now, lower tax in retirement | Lower earners now, higher tax expected later |
| 2026 limit | $24,500 combined (traditional + Roth) | |
Does a 401(k) reduce FICA taxes?
No. This is a common misconception. Traditional 401(k) contributions reduce your federal and state income tax — but FICA taxes (Social Security 6.2% and Medicare 1.45%) are calculated on your gross wages before any 401(k) deduction.
So on a $75,000 salary, you pay Social Security on the full $75,000 regardless of whether you contribute 0% or 15% to your 401(k). The FICA bill stays the same either way.
How to find your 401(k) on your pay stub
On your pay stub, look for a line item labeled "401(k)", "403(b)", "Retirement", or your employer's specific plan name. It will appear as a pre-tax deduction — listed after gross pay but before federal and state tax withholding.
Your federal and state taxable wages (the amounts used to calculate income tax withholding) will be lower than your gross wages by the amount of your 401(k) contribution. Your Social Security wages and Medicare wages will equal your full gross pay.
Frequently asked questions
Does contributing more to a 401(k) always make sense?
It depends on your situation. The tax savings are real and guaranteed, and employer matches (if offered) are essentially free money. However, if you have high-interest debt or no emergency fund, building those first may make more financial sense than maximising retirement contributions. At minimum, contribute enough to get your full employer match — that's an instant 50–100% return on your contribution.
When does the tax saving show up in my paycheck?
Immediately. Your employer calculates income tax withholding based on your reduced taxable wages from day one. You don't wait until April — the tax saving is built into every paycheck as soon as your 401(k) deduction starts.
What happens to my 401(k) if I change jobs?
Your 401(k) balance belongs to you (though employer match contributions may be subject to a vesting schedule). When you leave, you can roll the balance into your new employer's plan or an IRA — preserving the tax-deferred status and avoiding early withdrawal penalties.
How do I know how much to contribute?
A common starting point: contribute at least enough to get your full employer match (often 3–6% of salary). Then aim to increase to 10–15% of gross income over time. Use the PaycheckCrunch calculator to model the exact take-home impact of any contribution rate before you adjust your elections.