FICA Mechanics & Skepticism

Understanding the Terminology: A Section 125 plan, a cafeteria plan, and a Section 125 cafeteria plan are the same legal instrument. Section 125 of the Internal Revenue Code is the statute. A Premium Only Plan (POP) is the simplest cafeteria plan. Employers allow for eligible benefits to be pretaxed to reduce FICA obligations.

If you are evaluating a Self-Insured Medical Reimbursement Plan (SIMRP) or another pretax wellness arrangement, the decision usually turns on three questions:

• How a qualified pretax election reduces FICA wages without reducing the employee’s stated pay rate

• Whether the quoted savings can be rebuilt from your actual payroll file, employee by employee

• Whether every election and reimbursement stays inside the Code, with failed claims treated as wagesThe problem we see is that most companies only get line items without documentation.

The problem we see is that most companies only get deduction line items without documentation. This creates obvious compliance and tax risks. But you're also left without a proper understanding of the mechanics.

These savings are created through a set of coded values from the IRS. It operates on the same pretax mechanics as your health insurance or HSA so you just need to understand freshman algebra.

At Thrive Benefits Group we like to make this clear, easy to understand, and easy to implement. We model your exact dollar for dollar savings with the data you already run through payroll while maintaining compliance.

This article is about the mechanics. We'll go over how pretax elections affect employer FICA, further reduce employee federal and state income taxes, edge cases where yields change, and how to go from a payroll to predictable savings.

The Federal Insurance Contributions Act (FICA) are employer and employee taxes for social security and medicare. These are deducted from taxable wages every paycheck for all W2 empoyees.

The deduction employees see on their paycheck is matched equally by an employer contribution. So when an employee is taxed for every wage:

• Social Security (OASDI): 6.2%

• Medicare (HI): 1.45%

As an employer, you pay a 7.65% match on FICA-eligible gross wages up to the annual Social Security wage cap, and 1.45% on wages above that limit.

Here's a quick example for easy math:

That means for every $4000 paycheck, you match the combined $306 total which was deducted from their paycheck.

How Pretax Elections Create Savings

When employees elect to participate in a benefit which is pretaxed through a documented plan, their taxable wages decrease by the amount they pretaxed.

Let's use the same example above, but add a $1,000 pretax deduction.

That's a $76.50 decrease in what you're obligated to match in FICA for same paycheck.

In laymans terms, FICA liabilities decrease = .0765 x Pretaxed Amount.

Employee Tax Savings

We know that an employee reduces what they pay towards FICA at the same rate as their employer. Again, that's because the combined 7.65% rate between medicare and social security is matched.

But there are still federal and state taxes (unless you live in a state like TN or TX) that an employee is responsible for without an employer match.

Let's take the same employee paystub, now including federal and state taxes.

And now let's compare total taxes after the employee adds the same $1,000.00 pretax deduction

From a tax perspective, employees have much more to gain by deciding to pretax an eligible deduction that they would normally be taken out of their check anyway. Comparing the before and after results, you can see a $246.50 decrease in combined taxes.

Over the course of a year, this hypothetical employee would have saved $2,958 in taxes.

Edge cases that change the yield

While 7.65% is the standard baseline for employer FICA match savings, real-world variables can change those outcomes like wages. The Social Security Wage Cap ($184,500 for 2026)

Social Security tax (6.2%) caps once an employee reaches $184,500 in earnings within a calendar year. Both the employee and the employer stop paying the 6.2% Social Security tax.

That means employer FICA savings on additional pretax elections drop from 7.65% to 1.45% for the rest of the year.

Medicare tax on the other hand does not stop, in fact there's also Additional Medicare Tax (0.9% above $200,000).

There is no employer match on that 0.9%. The employer withholds it, but only the employee pays it. That changes the employee-side yield, not the employer 7.65% / 1.45% match:

A pretax election still reduces Medicare wages. Over $200,000, the employee therefore saves 1.45% plus 0.9% on the pretaxed amount, while the employer still saves only 1.45%.

Payroll starts withholding at $200,000 per employee. The employee’s actual tax can differ by filing status: $200,000 single, $250,000 married filing jointly, and $125,000 married filing separately.

From Payroll to Predictable Savings

The most critical element to create these savings is proper legal documentation. A pre-tax deduction isn’t just a setting or toggle inside your payroll software.

It requires a formal, written plan document legally adopted before elections begin for those tax savings to be valid.

Think of the deduction line item as the building and the plan document as the building permit. The building stands either way... until an inspector asks to see the paperwork. Without a written Section 125 Cafeteria Plan in place, any pre-tax treatment you've claimed can be retroactively disqualified during an IRS audit.

At Thrive Benefits Group, we remove this friction entirely: we provide, manage, and update all required plan documentation for our clients at no cost.

Once your legal foundation is established, turning raw payroll data into predictable tax savings takes zero heavy lifting.

All the information you need already lives inside your current payroll file. Here is how we bridge the gap:

• Step 1: Census Collection - We collect a simple, anonymized payroll report

• Step 2: Precision Savings Modeling - We run the math employee-by-employee

• Step 3: Seamless Payroll System Integration We map the new line items directly into your existing setup (ADP, Paychex, Gusto, QuickBooks, etc.), so you and your team can start saving.