HSA eligibility is binary: on the first day of any given month, you either qualify to contribute or you don't. The IRS rule has four parts, and getting any one of them wrong can erase a year's worth of tax savings or trigger a 6% excise tax. Here's the full checklist in plain English.
The Four IRS Eligibility Rules
To be HSA-eligible for a given month, all four of these must be true on the 1st of that month:
- You're covered by a qualifying High-Deductible Health Plan (HDHP).
- You have no other disqualifying health coverage.
- You're not enrolled in Medicare (any part).
- You can't be claimed as a dependent on someone else's tax return.
Miss any one of those and you're not eligible for that month — meaning you can't contribute, and any contributions made on your behalf become "excess" subject to a 6% annual excise tax until they're withdrawn.
Rule 1: What Qualifies as an HDHP for 2026?
Not every "high deductible" plan is an IRS-qualifying HDHP. The annual minimums and maximums change each year. For 2026:
| Plan Feature | Self-Only | Family |
|---|---|---|
| Minimum deductible | $1,700 | $3,400 |
| Maximum out-of-pocket | $8,500 | $17,000 |
| Annual contribution limit | $4,400 | $8,750 |
| Catch-up contribution (age 55+) | +$1,000 | +$1,000 |
The plan also can't pay for anything other than preventive care below the deductible. Telehealth that's free before the deductible has historically been a sticking point — the COVID-era safe harbor has come and gone several times, so check whether your plan's no-cost telehealth still preserves HDHP status. Full breakdown in the 2026 contribution limits guide.
Rule 2: Disqualifying "Other Coverage"
This is where most people slip. You can't have any health coverage that pays for medical expenses below the HDHP deductible. The common offenders:
- A general-purpose Health FSA — yours or your spouse's. Even if you don't use the FSA, simply being covered disqualifies you.
- A Health Reimbursement Arrangement (HRA) that pays for first-dollar care.
- A non-HDHP spouse's plan that covers you (e.g., as a dependent on their PPO).
- TRICARE — the IRS treats it as disqualifying coverage in essentially all cases.
- VA benefits used in the last 3 months (with an exception for service-connected disability and preventive care).
- Indian Health Service care received in the last 3 months (similar rules apply).
The good news: a Limited Purpose FSA (dental and vision only) and a post-deductible HRA are permitted alongside an HSA. So is a discount card, a wellness program with no actual medical reimbursement, or accident/disability insurance. For a full HSA-vs-FSA comparison see HSA vs FSA.
Rule 3: Medicare Disqualifies You
Once you're enrolled in any part of Medicare — A, B, C, or D — you can no longer contribute to an HSA. You can keep using the existing balance for qualified expenses forever, but new deposits stop. This catches a lot of people at age 65 because Part A is automatic and free if you're already drawing Social Security.
Worse, if you delay Medicare past 65 and later enroll, Part A is backdated up to six months. Any HSA contributions during that backdated window become excess. We have a full walkthrough in HSA + Medicare: The 6-Month Lookback Rule.
Rule 4: You Can't Be a Dependent
If your parent (or anyone else) can claim you as a dependent on their tax return, you're not HSA-eligible — even if you have your own HDHP and pay your own premium. This trips up adult children on a parent's plan up to age 26 who happen to be claimable as qualifying dependents.
Note: a dependent who is covered by a parent's HDHP can open their own HSA in some situations (the IRS treats a non-tax-dependent adult child differently). But if mom or dad checks the dependent box, your HSA is off-limits.
The Partial-Year Traps
HSA eligibility is determined month by month. If you become eligible mid-year, two things can happen:
- The "pro-rata" rule. Your contribution limit is the annual max times (eligible months / 12). Become eligible July 1 with self-only coverage and your 2026 limit is $4,400 × 6/12 = $2,200.
- The "last-month" rule. If you're HSA-eligible on December 1, you may contribute the full annual amount as long as you remain eligible through the end of the following year (the "testing period"). Lose eligibility during the testing period and the excess gets pulled back into income plus a 10% penalty.
If you switched jobs, married, divorced, or had a baby this year, the partial-year math matters. See switching jobs with an HSA, HSAs and marriage, having a baby with an HSA, and HSA mistakes after divorce for the specific scenarios.
The 5-Minute Self-Check
- Is my plan an IRS-qualifying HDHP? (Confirm with HR or the plan summary; deductible and OOP must hit the table above.)
- Am I covered by any general-purpose FSA, HRA, TRICARE, or non-HDHP plan — including through a spouse?
- Am I enrolled in any part of Medicare? Will I be in the next 6 months (Social Security backdating)?
- Could anyone claim me as a tax dependent?
- Did my coverage start or end mid-year? If so, do the pro-rata math.
Four no's plus a yes on rule 1 and you're eligible. If you're new to all this, start with What is an HSA and our HSA-eligible items directory. If you want to see how much the eligibility is actually worth in real dollars, run the numbers through the HSA ROI calculator.
The Bottom Line
HSA eligibility is strict, monthly, and unforgiving — but it's also fully knowable in five minutes. Run the four-rule check during open enrollment and again any time your coverage changes. If you qualify, contributing is one of the highest-return moves in the tax code. If you don't, fix the disqualifying piece (often as simple as a spouse's FSA election) before the next plan year.