Pre-Tax vs. After-Tax Deductions: What's the Difference?

Every deduction on your pay stub is either pre-tax or after-tax. A pre-tax deduction comes out of your pay before taxes are calculated, so it lowers your tax bill along with your take-home pay. An after-tax deduction comes out of pay that has already been taxed, so it lowers your take-home pay by the full amount and leaves your taxes unchanged. The same $100 can cost your paycheck anywhere from about $55 to $100 depending on which kind of deduction it is.

There's a second distinction that most guides skip: some pre-tax deductions avoid Social Security and Medicare tax and some don't. Health premiums paid through a cafeteria plan skip all three taxes; a traditional 401(k) contribution skips income tax but still pays the 7.65% for Social Security and Medicare. This guide sorts every common deduction into the right category, gives the 2026 limits, and works out what each one actually costs per $100.

The short version

Pre-tax deductions that also skip Social Security and Medicare: health, dental and vision premiums under a Section 125 plan; HSA contributions made through payroll; health and dependent care FSA contributions; and qualified transit and parking benefits. Pre-tax deductions that skip income tax only: traditional 401(k), 403(b), governmental 457(b) and the federal Thrift Savings Plan. After-tax deductions: Roth 401(k) and Roth 403(b) contributions, after-tax disability and supplemental life insurance, union dues, charitable payroll giving, wage garnishments and 401(k) loan repayments.

The table shows what happens to a $60,000 salary, single filer, no state income tax, when $3,000 a year goes to each type. All three options put the same $3,000 into a benefit or account. The traditional 401(k) costs about $2,640 of take-home pay, the Section 125 option about $2,411, and the Roth 401(k) the full $3,000.

How pre-tax deductions lower your taxes

A pre-tax deduction is taxed at your marginal rate, the rate on your last dollars of income, because it comes off the top. At $60,000, a single filer's taxable income after the $16,100 standard deduction is $43,900, which falls in the 12% federal bracket. Each pre-tax dollar saves 12 cents of federal income tax, plus the state rate if your state follows the federal treatment, plus 7.65 cents of FICA if it's a Section 125 deduction.

That's why the table of costs below depends on your bracket. In the 22% bracket with a 5% state tax, $100 to a traditional 401(k) costs $73 of take-home pay, and $100 of health premiums through payroll costs about $65.35. In the 10% bracket with no state tax, the same 401(k) dollar costs $90. Pre-tax savings are worth the most to people in higher brackets and in states with income tax.

Pre-tax deductions that skip FICA too

Section 125 of the tax code lets employers offer a cafeteria plan, under which certain benefits are paid with pay that's excluded from both income tax and Social Security and Medicare wages. Health, dental and vision premiums are the most common. If your employer offers insurance and takes your share of the premium out of your check, it's almost always under a Section 125 plan.

HSA contributions made through payroll are the best-treated money in the tax code. They skip federal income tax and FICA going in, grow tax-free, and come out tax-free for qualified medical expenses. You need a high-deductible health plan to contribute. The 2026 limits are $4,400 for self-only coverage and $8,750 for family coverage, plus $1,000 more if you're 55 or older. Contributing on your own and deducting it on your tax return saves income tax but not FICA, so payroll contributions are worth more.

Health FSAs let you set aside up to $3,400 in 2026 for medical costs, with the same tax treatment as HSA payroll contributions, but unused money is generally forfeited at year-end beyond a small carryover or grace period your plan may allow. Dependent care FSAs cover child care for children under 13 and some adult care; the limit rose to $7,500 per household starting in 2026. Qualified transit passes and parking can be paid pre-tax up to $340 a month each in 2026.

Pre-tax deductions that skip income tax only

Traditional 401(k), 403(b), 457(b) and Thrift Savings Plan contributions are excluded from federal income tax and most state income taxes, but Social Security and Medicare are still charged on them. The 2026 employee contribution limit is $24,500, with an extra $8,000 catch-up contribution at age 50 or older and a larger $11,250 catch-up at ages 60 through 63. Starting in 2026, workers whose prior-year wages from the employer exceeded about $150,000 must make catch-up contributions as Roth contributions.

The money isn't tax-free forever. Traditional contributions and their earnings are taxed as ordinary income when you withdraw them in retirement, so the deduction is really a deferral. The bet is that your tax rate will be lower in retirement than it is now, which is true for many workers but not all. Our 401(k) paycheck guide shows the per-check effect at several salaries.

See a $3,000 401(k) on a $60,000 paycheck →

After-tax deductions

Roth 401(k) and Roth 403(b) contributions are the most important after-tax deductions. They're taxed now, then grow and come out tax-free in retirement if you're at least 59½ and the account has been open five years. The same $24,500 limit is shared between traditional and Roth contributions; you can split it any way you like.

Some insurance is better paid after-tax. If you pay disability insurance premiums with after-tax money, any benefits you later receive are tax-free; if the premiums were pre-tax or paid by your employer, the benefits are taxable. Group-term life insurance works the other way: employer-paid coverage above $50,000 creates imputed income, an amount added to your taxable wages even though you never receive it as cash. Supplemental life insurance you buy through work is normally after-tax.

Union dues, charitable payroll giving, wage garnishments, child support orders, and repayments of a loan from your 401(k) are all after-tax. Loan repayments are after-tax even though the original contributions weren't, which is one reason 401(k) loans are more expensive than they look.

What $100 of each really costs

The table shows how much take-home pay $100 of each kind of deduction costs at each federal bracket, with no state tax and with a 5% state income tax. After-tax deductions always cost the full $100. For a traditional 401(k), subtract your marginal federal and state rates. For Section 125 benefits, also subtract 7.65% for Social Security and Medicare, as long as your pay is under the Social Security wage base.

Traditional or Roth?

The choice between traditional and Roth comes down to when you'd rather pay the tax. If your tax rate today is higher than you expect it to be in retirement, traditional contributions win: you deduct at a high rate now and pay at a lower rate later. If your rate today is lower than you expect later, Roth wins. People early in their careers, in the 10% or 12% brackets, often do better with Roth. People in the 24% bracket or above, especially in high-tax states they may leave in retirement, often do better with traditional.

Nobody knows future tax rates, so many people split contributions between the two to diversify. Roth money also has practical advantages: it doesn't count as taxable income in retirement, which can keep Social Security benefits and Medicare premiums lower, and Roth 401(k) accounts no longer have required minimum distributions during the owner's lifetime. The employer match is always made pre-tax unless your plan lets you choose Roth treatment for it.

Employer contributions

Money your employer puts in on your behalf is not part of your paycheck, but it follows the same tax rules. The employer's share of health insurance premiums is excluded from your wages entirely, which makes employer-paid health coverage one of the largest untaxed benefits most workers receive. Employer 401(k) matching contributions go in pre-tax and are taxed when withdrawn. Employer HSA contributions are tax-free and count toward your annual HSA limit, so if your employer contributes $1,000 to a self-only HSA, you can add up to $3,400 yourself in 2026.

The match deserves special attention. A common formula is 50% of your contributions up to 6% of pay. At $60,000, contributing 6% ($3,600) brings in a $1,800 match. Contributing 3% brings in only $900. No other financial decision on a pay stub returns 50% immediately, so contributing at least enough to get the full match is the first priority for most people, before deciding between traditional and Roth for the rest.

When you change jobs mid-year

Limits work differently for different accounts when you change jobs. The $24,500 401(k) employee limit is per person, not per employer, so contributions at both jobs together can't exceed it. Each new employer's payroll system doesn't know what you contributed at the last job, so you have to track it yourself and adjust. Excess contributions have to be withdrawn by April 15 of the next year to avoid being taxed twice.

HSA limits are also per person, and you can keep and spend from your HSA after leaving the job. Health FSAs are tied to the employer: money left in the account when you leave is generally forfeited unless you elect COBRA continuation for the FSA, so spend it down before your last day if you can. Social Security tax restarts at each new employer, so a high earner who changes jobs may have more than the maximum withheld across the two employers; the excess comes back as a credit on your tax return.

State exceptions

Most states follow the federal treatment of pre-tax deductions, but not all. Pennsylvania taxes employee 401(k) and 403(b) contributions for state income tax, so those contributions save federal tax only. Its local earned income taxes generally follow the same rule. California and New Jersey don't recognize HSAs, so HSA contributions are taxed for state purposes in those two states, and HSA earnings may be taxed at the state level too.

States without an income tax have nothing to reduce, so pre-tax deductions save federal tax and, for Section 125 benefits, FICA only. That makes the decision between traditional and Roth contributions a little more favorable to Roth for workers in Texas, Florida or Washington who plan to stay there in retirement.

Reading your pay stub

Pay stubs usually show two taxable wage figures: federal taxable wages and Social Security or Medicare wages. The difference between gross pay and federal taxable wages is your total pre-tax deductions. The difference between federal taxable wages and Social Security wages is your 401(k)-type deductions, which reduce income tax but not FICA. On your W-2, box 1 shows federal taxable wages and boxes 3 and 5 show Social Security and Medicare wages. If box 1 is lower than box 3, it's usually because of 401(k) contributions.

If a deduction is in the wrong place, such as a health premium being taken after tax when your employer offers a cafeteria plan, ask your payroll department. Fixing it mid-year can save hundreds of dollars.

Read our pay stub guide →

Common mistakes

The common mistakes are skipping the employer match, which is free money that no tax analysis beats; contributing to an HSA outside payroll and losing the FICA savings; over-funding a health FSA and forfeiting the remainder; assuming 401(k) contributions reduce Social Security tax; and forgetting that traditional 401(k) money will be taxed when it comes out. Another is judging a deduction by the amount on the stub instead of the change in take-home pay, which is always smaller for pre-tax deductions.

Run your own numbers

The paycheck calculator shows the effect of pre-tax deductions on every line of your check. The FICA calculator separates Section 125 deductions so you can see how much Social Security and Medicare tax they save, and the net to gross calculator shows the salary you'd need to keep the same take-home pay after starting a new deduction.

See how much FICA a $3,000 premium saves →