401(k) Match Math: When Your Employer Is Probably Lying

Your employer says “we match 100% up to 6%”. You assume that means if you contribute $6,000, you get $6,000 back. The marketing slide says exactly that.

The marketing slide leaves out three things, and any one of them can cut your match by 50% in a year.

Trick 1: per-paycheck cap, not annual

Most 401(k) plans match per pay period, not per year. If you contribute 12% of each paycheck and they match up to 6% — but you front-load to hit the IRS limit ($23,000 in 2026) by July — they only matched the 6% in the first paychecks. The remaining $11,500 you contributed got zero match because their formula already paid out for the year.

Reach the cap evenly across 26 pay periods, not in 13. The math:

• Salary $200K, IRS cap $23K → 11.5% per paycheck (steady).
• Anything front-loaded above 6% per paycheck before mid-year forfeits future match.

Companies with “true-up” provisions fix this — they recalculate annually and pay you the missed match in February. About 40% of plans have it. The other 60% don’t and don’t volunteer this fact.

Ask HR: “Does our plan have a true-up?” Get the answer in writing.

Trick 2: vesting schedule

“100% match” doesn’t mean you keep 100% if you leave. Most plans vest the match over 3–6 years on a graded schedule:

Years at company	Vested %
< 1 year	0%
1–2 years	20%
2–3 years	40%
3–4 years	60%
4–5 years	80%
5+ years	100%

If you leave at year 2.5 with $30K of employer match contributions, you keep $12K. The other $18K goes back to the company. This is legal, disclosed in the SPD (Summary Plan Description) you didn’t read, and never mentioned in recruiting.

If you’re considering an offer and your sign-on bonus has a 1-year clawback, look at the unvested 401(k) match too. A “$50K signing bonus” can be net negative if you forfeit $80K in unvested match by leaving early.

Trick 3: highly compensated employee (HCE) clawback

If you earn over ~$155K (2026 IRS threshold), you’re an HCE. If your company’s plan fails non-discrimination testing — meaning the lower-paid employees didn’t contribute enough — the IRS forces them to return a chunk of HCE contributions in March, with the matching contributions also reduced.

This isn’t your fault. It’s not predictable. It happens to about 15% of plans annually. If it happens to yours, you get a check in March for the excess plus a 1099-R, and you owe taxes on it as ordinary income that year.

Mitigation: ask HR if your plan is a safe harbor plan. Safe harbor plans are exempt from the test. About 70% of companies use them. The other 30% are a roulette wheel.

What to actually do

1. Read your SPD. Search for: “match formula”, “vesting”, “true-up”, “safe harbor”. 4 minutes. Skipped by 90% of employees.
2. Set your contribution to evenly distribute across the year (use the per-paycheck calculator your provider has).
3. Track your vesting cliff. If you’re leaving within 6 months of crossing a vesting tier, postpone if you can. The math often beats a 10% pay raise.
4. If you’re an HCE in a non-safe-harbor plan, expect refunds. Don’t spend the full match before March.

The “free money” framing is correct, with a footnote

Yes, it’s still the best deal in compensation. Yes, you should max the match even if your fund options are bad — the match alone is usually a 50% instant return on your contribution. But “free” is the wrong word. It’s conditional money, gated by mechanics most employees don’t know about until they cost them something.

Now you do. Don’t be the colleague who finds out in March.

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This is informational. For your specific situation, talk to a fee-only financial planner, not the 401(k) call center.