Almost every tax-advantaged account makes you choose your tax break. A traditional 401(k) gives you a deduction now but taxes every dollar on the way out. A Roth gives you tax-free withdrawals but no deduction today. The HSA refuses to choose. Contributions are deductible (or pre-tax through payroll), the balance grows with no tax on interest, dividends, or gains, and withdrawals are completely tax-free as long as they pay for qualified medical expenses. Three tax breaks in one account. Nothing else in the code does that.

For 2026, the IRS set the contribution limits at $4,400 for someone with self-only high-deductible coverage and $8,750 for a family, under Revenue Procedure 2025-19. Anyone 55 or older can add a $1,000 catch-up on top. To contribute at all, you have to be covered by a qualifying high-deductible health plan — for 2026 that means a deductible of at least $1,700 for self-only coverage or $3,400 for a family, with out-of-pocket maximums capped at $8,500 and $17,000 respectively. If you have a spouse who is also 55-plus, note that each catch-up has to go into that person's own HSA, not one shared account.

Here is the insight that separates people who build six-figure HSA balances from people who never get above a few thousand dollars: you do not have to spend the money the year you contribute. The IRS imposes no deadline. If you pay a $400 doctor bill out of your regular checking account today and keep the receipt, you can reimburse yourself from the HSA 1, 10, or 25 years from now — and in the meantime that $400 stays invested and compounding tax-free. People who treat the HSA as a long-term investment account and pay current medical costs from cash are effectively building a second Roth IRA, one with an even better tax profile.

The math compounds quietly. A 50-year-old who maxes a family HSA at roughly $9,750 a year (including the catch-up) and earns 7 percent could be looking at well over $200,000 by 65 — every dollar of it available tax-free for the medical and long-term-care costs that tend to balloon late in life. Fidelity's widely cited estimate is that an average 65-year-old couple retiring today will spend somewhere around $330,000 on health care over the rest of their lives. The HSA is purpose-built to meet exactly that bill with untaxed dollars.

The catch — and it is a real one — is Medicare. The moment you enroll in any part of Medicare, you lose the ability to make new HSA contributions. Most people enroll at 65, and Medicare Part A enrollment can even apply retroactively up to six months when you sign up after 65, which can create an inadvertent over-contribution if you are not paying attention. So the practical planning window is the stretch of working years before 65. If you are 60 and still on a high-deductible plan, those last few years are the time to max it aggressively. You can still spend an HSA tax-free after 65 — you just cannot add to it.

After 65 the rules also loosen in a useful way. Before 65, a non-medical withdrawal is taxed and hit with a 20 percent penalty. Once you turn 65, that penalty disappears entirely — a non-medical withdrawal is simply taxed as ordinary income, exactly like a traditional IRA distribution. So in the worst case, your HSA behaves like a traditional IRA, and in the likely case (you will have medical and long-term-care expenses), it behaves better than a Roth. There is almost no scenario where the account hurts you.

One more retirement-specific wrinkle: once you are on Medicare, your HSA can pay your Medicare Part B, Part D, and Medicare Advantage premiums tax-free — and at 2026 rates, with the standard Part B premium at $202.90 a month, that is real money. It cannot, however, pay Medigap (Medicare Supplement) premiums. It can also cover a portion of long-term-care insurance premiums, with the deductible amount rising by age. These are precisely the bills retirees actually face, which is what makes a well-funded HSA so valuable late in the game.

If you are still working and covered by a high-deductible plan, treat the HSA as the first account you max, ahead of even the 401(k) match in some cases, because no other dollar gets all three tax breaks. Invest the balance rather than leaving it in cash, and pay routine medical bills from your checking account if your budget allows.

Keep a digital folder of every medical receipt you do not reimburse immediately. That paper trail is what lets you pull tax-free money out decades later — it is the difference between a spending account and a tax-free retirement fund. A scanned photo in a labeled cloud folder is enough.

If you are approaching 65, map your Medicare enrollment date carefully and stop HSA contributions in time to avoid an excess-contribution penalty, accounting for the up-to-six-month retroactive Part A start. Front-load your contributions in the final pre-Medicare years so the account is as large as possible before the door closes.

• Leaving the entire balance in cash. An uninvested HSA forfeits the tax-free growth that is the whole point — most custodians let you invest above a small cash threshold.
• Spending it down every year for routine costs instead of paying from cash and letting the account compound for the expensive years later in retirement.
• Contributing after enrolling in Medicare, including the retroactive Part A trap, which creates a 6 percent excess-contribution excise tax until corrected.
• Throwing away medical receipts. Without them you lose the ability to reimburse yourself tax-free in future years.
• Trying to pay Medigap premiums from the HSA tax-free — Part B, Part D, and Advantage premiums qualify, but Medicare Supplement premiums do not.