HSA Comparability Rules: What Employers Need to Know

HSA comparability rules apply only when you contribute to employees' HSAs outside a Section 125 cafeteria plan. They require essentially identical contributions to every comparable employee, and the penalty for getting it wrong is a 35% excise tax on your total HSA contributions for the year. The practical takeaway is simpler than the rules: route employer contributions through a cafeteria plan, and comparability doesn't apply at all.

When Comparability Applies — and When It Doesn't

There are two legal lanes for employer HSA contributions, and every dollar you contribute travels in exactly one of them:

1. Outside a cafeteria plan — you simply deposit money into employees' HSAs, with no employee election involved. These contributions are governed by the comparability rules under Section 4980G.
2. Through a cafeteria plan — employer contributions are made under your Section 125 plan (including any arrangement where employees can make pre-tax HSA elections alongside employer dollars). These are exempt from comparability and governed instead by Section 125 nondiscrimination testing, which is considerably more flexible.

Most employers are in lane two, sometimes without realizing that's what protects them. If you already have a cafeteria plan with HSA payroll deferrals and your contributions run under it, comparability likely isn't your problem — Section 125 testing is. The trap is the employer who writes seed checks or bonus deposits into HSAs outside any plan structure, assuming goodwill is a compliance strategy.

What "Comparable" Means

If you're in the comparability lane, contributions must be the same for all comparable participating employees: either the same dollar amount or the same percentage of the HDHP deductible.

"Comparable" is defined by categories. You may treat these groups separately:

• Employment status: current full-time, current part-time (customarily under 30 hours/week), and former employees are distinct categories.
• Coverage tier: self-only versus family coverage can receive different amounts, and tiers of family coverage (self+one, self+two, self+family) may be treated as separate categories — with the constraint that a higher tier can't receive less than a lower one.
• Non-HDHP employees: employees not on your HDHP (or not HSA-eligible) simply aren't in the comparison.

There's one deliberate asymmetry: employers may contribute more to non-highly compensated employees than to highly compensated ones. The reverse is prohibited. You can favor the shop floor over the C-suite, never the other way around.

What you can't do outside a cafeteria plan is nearly everything employers actually want to do: match employee contributions (the match varies with behavior), reward tenure or performance, contribute per division or per manager's discretion, or make wellness-linked contributions. Any variation between comparable employees — even $1,000 versus $990 — is a violation.

The 35% Excise Tax

The penalty is what makes this rule worth taking seriously. Fail comparability, and the excise tax is 35% of the aggregate amount you contributed to all employees' HSAs during the year — not 35% of the discriminatory sliver.

Illustration: a 50-person company contributes $1,000 to each employee's HSA outside a cafeteria plan — but gives three executives $2,000 instead, for $53,000 total. The excise tax isn't 35% of the extra $3,000. It's 35% of the full contribution pool: $18,550, on a $53,000 program, for a $3,000 design mistake. It's reported on Form 8928, and it's not deductible.

That severity is intentional — and it's why the rules effectively function as a fence pushing employers toward the cafeteria plan lane.

Why Most Employers Route Through a Cafeteria Plan

Inside a Section 125 plan, the comparability rules are switched off entirely, and the design space opens up:

• Matching contributions become possible — the design that best converts employer dollars into employee participation (see contribution strategies)
• Wellness-linked and variable designs can work, subject to Section 125 testing and wellness-program rules
• Testing is aggregate and flexible — Section 125 nondiscrimination testing looks at whether the plan disproportionately favors highly compensated and key employees, rather than demanding identical amounts per person

The cafeteria plan route has its own requirements — a written plan document adopted in advance, annual nondiscrimination testing — but those are things a well-run benefits program needs anyway. The marginal cost of doing employer HSA contributions correctly is close to zero if your Section 125 house is in order.

None of this is tax advice, and the boundary cases (partial-year eligibility, mid-year hires, former employees) have real texture — worth confirming your design with benefits counsel or your administrator.

Practical Checklist

1. Identify your lane. Are employer HSA contributions made under your cafeteria plan document, or outside any plan? If you're not sure, that's the first thing to resolve.
2. If outside: confirm every comparable employee (by status and coverage tier) receives the same dollar amount or same percentage of deductible. Kill any matches, discretionary amounts, or incentive-linked contributions — or move them inside the plan.
3. If inside (recommended): confirm the plan document actually provides for employer HSA contributions, and amend it if it predates your HSA program.
4. Run Section 125 nondiscrimination testing annually. Routing through the plan trades comparability for testing — it doesn't trade it for nothing.
5. Verify eligibility before contributing. Only HSA-eligible employees — on a qualifying HDHP, no disqualifying coverage — can receive contributions in either lane.
6. Reconcile and report. All employer contributions land on the W-2 in Box 12, code W, and count against the 2026 limits ($4,400 / $8,750, +$1,000 catch-up).

How Hammock Helps

Hammock administers employer HSA contributions in whatever structure you run — flat seeds, tiered amounts, matches through your cafeteria plan — with payroll integrations, contribution-limit monitoring, eligibility checks, and accurate W-2 Box 12 reporting. Compliance support is part of administration, not an upsell.

And because the point of contributing is participation, Hammock makes the accounts worth funding: LMN pre-authorization applied at swipe turns gym, supplements, and recovery into qualified expenses, with individual clinical evaluation per participant, documented and audit-ready. At one $1B tech company, that lifted committed contributions 38% per participant, with employer FICA savings of $234 per employee per year measured across total elections.

FAQ

Do comparability rules apply if we only offer payroll deferrals?

If employees contribute their own money through your cafeteria plan and you contribute nothing, comparability doesn't come into play. It governs employer contributions made outside a cafeteria plan.

Can we give different HSA amounts to employees with family vs. individual coverage?

Yes, in both lanes. Under comparability, self-only and family tiers are separate categories, and family tiers may receive more — just be consistent within each tier.

Can we match HSA contributions without violating comparability?

Not outside a cafeteria plan — a match inherently varies by employee behavior, which comparability prohibits. Run the match through a Section 125 plan, where comparability doesn't apply.

What's the penalty for failing comparability?

An excise tax equal to 35% of all employer HSA contributions for the calendar year — the whole pool, not just the non-comparable portion — reported on Form 8928.

The Bottom Line

Comparability rules are rigid, the penalty is disproportionate, and the escape hatch is standing right there: a Section 125 cafeteria plan, which most employers need anyway. Know which lane your employer contributions travel in, keep the plan document current, run the annual testing — and then spend your attention on the thing that actually determines your program's ROI: getting employees to fund the accounts.

Want a second set of eyes on your contribution structure? Talk to our team.