Salary sacrifice arrangements in the United States
Reviewed by Mellow Editorial Team, HR & payroll content team
Salary sacrifice — known in the US as a salary reduction arrangement or pre-tax benefit election — lets employees redirect a portion of their gross wages toward qualifying benefits before payroll taxes are calculated. Both employee and employer pay less in FICA taxes on the redirected amount, making these arrangements genuinely valuable for both sides.
What "salary sacrifice" actually means in a US context
The term "salary sacrifice" is a British phrase. In the US, the same concept operates under Section 125 of the Internal Revenue Code, which governs cafeteria plans, and under other specific IRC provisions (such as Section 401(k) for retirement, Section 129 for dependent care, and Section 132 for commuter benefits).
The mechanics are straightforward: an employee agrees, before the pay period begins, to receive a lower cash salary in exchange for employer-provided benefits funded from that reduction. Because the benefit is technically an employer contribution — not wages — it is excluded from the employee's taxable income.
This is not voluntary after-the-fact spending. The election must be made prospectively, typically during open enrollment or at a qualifying life event. You cannot retroactively restructure wages already earned.
Which benefits can be run through a salary reduction arrangement
The most common categories employers use:
- Health, dental, and vision premiums under a Section 125 cafeteria plan. Employees elect to pay their share of premiums pre-tax, reducing federal income tax withholding and FICA on those amounts.
- Flexible Spending Accounts (FSAs) for healthcare or dependent care expenses.
- 401(k) and 403(b) retirement contributions. Employee deferrals reduce federal income tax withholding but are still subject to Social Security and Medicare taxes — an important distinction from the UK equivalent.
- Health Savings Accounts (HSAs) for employees enrolled in a qualifying high-deductible health plan.
- Commuter benefits under Section 132, covering transit passes and qualified parking.
Each category has its own IRC authority, its own limits, and its own rules about what counts as a qualifying expense. A Section 125 plan requires a written plan document; without one, benefits offered as pre-tax elections are not legally compliant.
The employer process, step by step
1. Draft and adopt a written plan document. A Section 125 cafeteria plan must be formally documented before any pre-tax elections take effect. The document defines eligible employees, benefit options, election windows, and the plan year. Most employers work with a third-party administrator (TPA) or benefits counsel to prepare this.
2. Set your open enrollment window. Employees make their elections before the plan year begins. Mid-year changes are only permitted after a qualifying life event (marriage, birth, loss of other coverage, and similar events defined in Treasury regulations).
3. Collect signed election forms. Document each employee's pre-tax election amount per benefit category. This is your authorization to reduce their cash wages accordingly.
4. Configure your payroll system. Pre-tax deductions must be coded correctly so the payroll engine reduces taxable gross before calculating federal income tax withholding (Form W-4 governs the withholding rate) and before calculating FICA — Social Security at 6.2% on wages up to the annual wage base, Medicare at 1.45% with no cap, plus the 0.9% Additional Medicare Tax on high earners. Health, dental, vision, FSA, HSA, and commuter deductions generally reduce both income tax and FICA bases. Standard 401(k) deferrals reduce income tax withholding but not FICA.
5. Remit the employer FICA match on the reduced wage base. Because the employee's taxable wages are lower, your matching FICA obligation — 6.2% Social Security plus 1.45% Medicare — is calculated on a smaller number. That is the direct cost saving to the employer.
6. Report correctly at year-end. The employee's Form W-2 must reflect the reduced taxable wages, with specific boxes used to report 401(k) deferrals (Box 12, Code D), employer HSA contributions (Box 12, Code W), and dependent care FSA amounts (Box 10). W-2s must reach employees and the Social Security Administration by January 31. File Form 941 quarterly, showing the reduced taxable wages and FICA calculations.
State tax treatment varies
Federal law allows the exclusion, but states do not all follow it automatically. Most states conform to IRC Section 125, so health premiums and FSA elections are also excluded from state taxable wages. Some states do not conform for certain benefits — California, for example, taxes employer HSA contributions differently from federal rules. If you operate in multiple states, verify each state's conformity before assuming the full pre-tax treatment applies.
Common compliance mistakes to avoid
Running salary reduction arrangements without a written plan document is the most frequent error and exposes the employer to back taxes and penalties. Other pitfalls include allowing employees to change elections mid-year without a qualifying event, failing to apply the correct use-it-or-lose-it rules for FSAs, and miscoding deductions in payroll so that FICA is calculated on the pre-reduction amount. If you run payroll across multiple jurisdictions, the complexity compounds quickly — a point worth considering when evaluating how Mellow runs payroll across six countries on one platform.
Nondiscrimination testing is also required for Section 125 plans, 401(k) plans, and dependent care FSAs. Highly compensated and key employees face benefit caps if the plan fails its annual test, so testing should be built into your plan year calendar, not treated as an afterthought.
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