What Is the Section 125 Tax Code and How Does It Work?

A Section 125 plan is an employer-sponsored arrangement that lets you pay for certain benefits with pre-tax dollars, lowering your federal income tax and your Social Security and Medicare taxes on every dollar you redirect. It takes its name from Section 125 of the Internal Revenue Code, which carves out an exception to the rule that any money you could have taken as cash counts as taxable wages. Because your election under the plan is locked in before the year starts, the IRS treats the redirected money as if it were never yours to begin with, so it never shows up as wages for federal income tax, Social Security, or Medicare purposes.¹ These arrangements are also called cafeteria plans, because you choose from a menu of qualified benefits.

What You Actually Save

Every dollar you route through a Section 125 plan skips three taxes: federal income tax at your marginal rate, the 6.2% Social Security tax, and the 1.45% Medicare tax. Depending on your bracket and where you live, that typically works out to somewhere between 20% and 40% back on each dollar.

A concrete example. If you’re in the 22% federal bracket and you put $3,400 into a health flexible spending account, you avoid about $850 in federal income tax and another $260 in FICA on that contribution. You never see the money on your paycheck, and you never see it on your W-2 as wages.

One boundary worth knowing before you plan around this: a handful of states don’t fully follow the federal treatment, so you may still owe state income tax on some or all of your salary reductions. Check your state’s rules rather than assuming the money is completely tax-free everywhere.

Which Benefits You Can Pay for Pre-Tax

Not everything qualifies. To be offered through a Section 125 plan, a benefit has to be specifically excludable from your gross income under another part of the tax code. The common ones:

Medical, dental, and vision insurance premiums you’d otherwise pay out of your paycheck.
Health Flexible Spending Accounts for out-of-pocket medical expenses.
Dependent Care Assistance Programs for eligible childcare or adult dependent care.
Group-term life insurance, with coverage up to $50,000 fully excludable and coverage above that taxable based on an IRS premium table.²
Adoption assistance for qualified expenses.
Employer contributions to your Health Savings Account, when you’re enrolled in a high-deductible health plan.

Several things are specifically barred. Long-term care insurance cannot go through a cafeteria plan. Neither can scholarships, educational assistance, or most fringe benefits under Section 132. Marketplace health plans purchased through the ACA exchanges generally can’t be included either, with a narrow exception for certain small employers.¹

The Two Structures Employers Use

Most Section 125 plans come in one of two flavors. A Premium Only Plan does one thing: it lets you pay your share of health, dental, and vision insurance premiums pre-tax. No FSAs, no dependent care account, minimal paperwork. If your employer’s plan feels invisible and all you notice is that your insurance premiums come out before taxes, you’re probably in a POP.

A Full Cafeteria Plan bundles the premium piece with additional benefits like Health FSAs, Dependent Care Assistance Programs, adoption assistance, and group-term life. More moving parts, more elections to make each year, and each component carries its own contribution limits and rules.

Locking In Your Election

Before each plan year, you decide how much salary to redirect and which benefits to fund. That election has to be in writing, and it’s generally locked in for the whole plan year. The lock is what makes the tax break work: because you can’t change your mind and take the cash instead, the IRS accepts that the money was never really yours.¹

Mid-year changes are only allowed if you have a qualifying life event and your plan document specifically permits the change. The IRS recognizes several categories:³

A change in marital status: marriage, divorce, legal separation, annulment, or the death of a spouse.
A change in the number of dependents: birth, adoption, placement for adoption, or the death of a dependent.
A change in employment status that affects health plan eligibility, including you, your spouse, or a dependent starting or stopping work, switching between full-time and part-time, or going on unpaid leave.
A dependent aging out of coverage or gaining eligibility under another plan.
Events that trigger HIPAA special enrollment rights, like losing other coverage or gaining a new dependent.

The change also has to be consistent with the event. A divorce might justify dropping a former spouse from your health plan; it wouldn’t justify adding a vision benefit you’d previously turned down. Most plans give you 30 days from the event to request the change, though the exact window is set by your employer’s plan document, not the IRS.

Financial hardship is not a qualifying event. If your budget gets tight mid-year, you still can’t reduce or stop your FSA contributions to free up cash. This is the single most common source of frustration employees have with these plans, and it’s worth going in with your eyes open.

Flexible Spending Accounts

FSAs are the part of a cafeteria plan that needs the most active management, because unused money can be forfeited at year-end.

Health FSA

A Health FSA reimburses out-of-pocket medical, dental, and vision expenses not covered by insurance. For plan year 2026, the maximum employee contribution is $3,400.⁴ The IRS adjusts this limit for inflation each year.

One quirk works strongly in your favor. Health FSAs run under the uniform coverage rule: your full annual election is available for reimbursement from day one of the plan year, no matter how little you’ve actually contributed. Elect $3,400, run up $3,000 in medical bills in January after only $280 has come out of your paychecks, and the plan still has to reimburse the full $3,000. If you leave the job before your contributions catch up, the employer absorbs the loss.

Dependent Care FSA

A Dependent Care Assistance Program covers care expenses that allow you to work, including daycare, preschool, after-school programs, and elder care. The statutory limit is $7,500 per household, or $3,750 if you’re married and filing separately.⁵ Unlike a Health FSA, this one has no uniform coverage rule: you can only be reimbursed up to what you’ve actually contributed so far.

Use It or Lose It

Both FSAs are subject to the use-it-or-lose-it rule: money left in the account at the end of the plan year is forfeited to the employer. The IRS lets employers soften this with one of two relief options, but a plan can’t offer both at once:

A grace period of an extra two and a half months after the plan year ends to incur eligible expenses. For a calendar-year plan, that means expenses through March 15 of the following year still count. Available for both Health and Dependent Care FSAs.⁶
A carryover, available for Health FSAs only. For plan years beginning in 2026, up to $680 of unused funds can roll into the next plan year. Your employer can set a lower cap.⁴

Overestimating in October and forfeiting hundreds of dollars in December is the most common mistake people make with FSAs. Base your election on predictable recurring costs like monthly prescriptions, regular copays, or scheduled dental work, and treat anything speculative as a bonus reason to spend down late in the year rather than a reason to contribute more.

If You Have an HSA Too

If your employer offers a high-deductible health plan paired with a Health Savings Account, a regular Health FSA will disqualify you from contributing to the HSA. The IRS treats a traditional Health FSA as “other health coverage” because it reimburses medical expenses below the HDHP deductible.⁷

The workaround is a limited-purpose FSA, which restricts reimbursements to dental and vision expenses. Because the IRS specifically disregards dental and vision coverage for HSA eligibility, a limited-purpose FSA lets you keep contributing to your HSA and still get a pre-tax benefit on those out-of-pocket eye exams and cleanings.⁸ The 2026 limit is the same $3,400 as a regular Health FSA, and the $680 carryover still applies.

Dependent Care FSAs don’t affect HSA eligibility at all, because they cover childcare and elder care rather than medical expenses. You can run both without any conflict.

What Happens When You Leave the Job

Terminating mid-year raises immediate questions about your balances. For a Health FSA, you can only submit claims for expenses incurred before your termination date, and only while you’re current on contributions. Any remaining balance after your final claims is forfeited. On the flip side, if you’d already been reimbursed for more than you’d contributed (which the uniform coverage rule makes possible), the employer can’t come after you for the difference.

Health FSAs are technically subject to COBRA. If you have a positive balance when you leave, your employer has to offer you the option to continue the FSA through the end of the plan year by paying the full contribution yourself, including whatever the employer had been covering. In practice, COBRA for an FSA rarely pencils out unless you have significant known medical expenses coming, because you’re paying with after-tax dollars and losing the point of the arrangement.

Dependent Care FSAs aren’t subject to COBRA. You can still submit claims for eligible expenses incurred during the plan year, up to what you’d already contributed through payroll deductions before your last day.

1
Office of the Law Revision Counsel. 26 USC 125 Cafeteria Plans
2
Internal Revenue Service. Group-Term Life Insurance
3
eCFR. 26 CFR 1.125-4 Permitted Election Changes
4
FSAFEDS. New 2026 Maximum Limit Updates
5
Office of the Law Revision Counsel. 26 USC 129 Dependent Care Assistance Programs
6
Internal Revenue Service. Eligible Employees Can Use Tax-Free Dollars for Medical Expenses
7
Office of the Law Revision Counsel. 26 USC 223 Health Savings Accounts
8
Internal Revenue Service. Publication 969 Health Savings Accounts and Other Tax-Favored Health Plans