Is Section 125 Pre Tax? Which Taxes It Skips, Which It Does Not, and What You Save

• Section 125 benefits are not subject to federal income tax withholding, Social Security tax or Medicare tax, per IRS Publication 15-B (2026).
• Employee Social Security tax is 6.2% and Medicare tax is 1.45%, so each $1,000 paid through Section 125 saves $76.50 in payroll tax, per IRS Tax Topic 751 (2026).
• A 401(k) deferral is still wages for Social Security and Medicare, so it saves income tax only, per IRS Tax Topic 424 (2026).
• In the worked example below, $3,180 of Section 125 benefits and a $3,000 401(k) save $984.87 a year for a $55,000 earner in the 12% bracket, using 2026 IRS rates.
• Social Security tax applies to the first $184,500 of wages in 2026, per the Social Security Administration (October 2025).

You are looking at a pay stub with five deductions and you want to know which ones are pre tax. Section 125 deductions are, and they skip more taxes than most other pre-tax money. This page shows what each deduction does to your taxes and where the exceptions are.

Reviewed by a licensed benefits professional. Last reviewed: October 5, 2026.

Is Section 125 pre tax?

Section 125 is pre tax. Money you pay for benefits through a Section 125 cafeteria plan is taken from your pay before tax is figured on it.

IRS Publication 15-B (2026) says qualified cafeteria plan benefits are not subject to federal income tax withholding, Social Security tax, Medicare tax or federal unemployment tax. The deduction on your pay stub may be labeled Sec 125, Cafe 125 or Section 125. Benecor Health's guide to what Sec 125 on a W-2 means→ shows how those labels connect to your tax form.

What taxes does a Section 125 deduction skip?

A Section 125 deduction skips three federal taxes: income tax, Social Security tax and Medicare tax. That is why it lowers three different boxes on your W-2.

IRS Tax Topic 751 (2026) sets employee Social Security tax at 6.2% and Medicare tax at 1.45%, which is 7.65% together. Your employer saves the same 7.65% on its side. Social Security tax stops once wages pass $184,500 in 2026, per the Social Security Administration.

Which pay stub deductions are pre tax, and which are not?

Section 125 deductions are pre tax for all three federal taxes. A 401(k) is pre tax for income tax only, and a Roth 401(k) is after tax.

IRS Tax Topic 424 (2026) says a 401(k) deferral is still included as wages subject to Social Security and Medicare withholding. That is the main reason a Section 125 dollar saves more than a 401(k) dollar. Retirement saving still has its own tax benefit, so this is not a reason to skip it.

Benecor's guide to the health pre-tax deduction code→ covers the paystub labels in more detail.

How much does a Section 125 deduction save me?

A Section 125 deduction saves 7.65% in payroll tax plus your income tax rate on every dollar. In the 12% bracket that is $196.50 per $1,000.

Here is a worked example. It is hypothetical and uses 2026 rates. A single worker earns $55,000. The worker pays $1,440 for medical, which is the 2025 KFF average worker share of single coverage, $240 for dental and puts $1,500 into an HSA through payroll. The worker also defers $3,000 into a traditional 401(k).

1. Section 125 total: $1,440 + $240 + $1,500 = $3,180.
2. Box 3 and 5 wages: $55,000 minus $3,180 = $51,820.
3. Box 1 wages: $55,000 minus $3,180 minus $3,000 = $48,820.
4. Taxable income: $48,820 minus the $16,100 single standard deduction = $32,720, which is in the 12% bracket (IRS, 2026 inflation adjustments).
5. Payroll tax saved on Section 125: $3,180 x 7.65% = $243.27.
6. Income tax saved on Section 125: $3,180 x 12% = $381.60.
7. Income tax saved on the 401(k): $3,000 x 12% = $360.00.
8. Total tax saved: $243.27 + $381.60 + $360.00 = $984.87 a year.

Per $1,000, the Section 125 money saved $196.50 and the 401(k) money saved $120.00. State income tax savings would add to both in most states.

Is a Section 125 deduction a tax deduction I claim on my return?

No. You do not claim it on your tax return. The tax break has already happened at payroll, because your employer left the amount out of your Box 1, 3 and 5 wages.

IRS Publication 15-B (2026) says excluded cafeteria plan benefits are not reported as wages. If you paid the same premium with after-tax money outside the plan, you would have to try to deduct it yourself, and most people cannot. This is the main reason the plan exists.

Is Section 125 taxable in my state?

Most states follow the federal exclusion, but not all of them do for every benefit. California is the clearest exception for HSA money.

The California Franchise Tax Board's 2025 Schedule CA (540) instructions say California law does not conform to the federal HSA deduction, and they tell filers to add employer HSA contributions from W-2 Box 12 code W back into California income. So in California, the HSA part of your Section 125 total is still taxed by the state. Your W-2 Box 16 shows state wages, and comparing it to Box 1 is a quick way to see if your state taxed more than the federal government did. For other states, check with your state tax agency, because this guide does not list every state rule.

Can I stop a Section 125 deduction I did not choose?

Usually not in the middle of the year. Section 125 elections are generally locked for the plan year, and mid-year changes are allowed only for specific events under 26 CFR 1.125-4.

Qualifying events include marriage, divorce, a birth or a change in employment status. Benecor's guide to Section 125 qualifying life events→ lists them. Your next open enrollment is the usual time to change an election.

What should I ask HR about my pre-tax deductions?

Ask HR which deductions are Section 125, which are not, and what each one buys you. A written answer gives you a record.

If you still cannot match a deduction to a benefit you chose, request a case review→ with a Benecor benefits expert. Employers can read the other side of this topic in Summit Health Benefits' guide to FICA tax savings from pre-tax benefits↗. For the full plan overview, see Benecor's Section 125 cafeteria plan guide→, and for the legal basis, see the Section 125 tax code→ explainer.

Sources: IRS Publication 15-B, Employer's Tax Guide to Fringe Benefits (2026); IRS Tax Topic 751, Social Security and Medicare withholding rates (2026); IRS Tax Topic 424, 401(k) plans (2026); IRS, 2026 tax inflation adjustments (2025); Social Security Administration, 2026 taxable wage base announcement (October 2025); 26 CFR 1.125-4, Permitted election changes (2026); California Franchise Tax Board, 2025 Instructions for Schedule CA (540) (2025); KFF, 2025 Employer Health Benefits Survey (2025).