What is an HSA, and why is it called triple tax-advantaged?

A Health Savings Account (HSA) is a savings account for medical expenses, available to people enrolled in a high-deductible health plan (HDHP). It's called triple tax-advantaged because it gets three tax breaks at once:

Contributions go in untaxed. They're tax-deductible, or taken from your pay before tax.
Growth is untaxed. Interest and investment gains inside the account aren't taxed.
Withdrawals are untaxed when they're used for qualified medical expenses.

No other US savings account gets all three. A traditional 401(k) gives you the first two but taxes withdrawals. A Roth IRA gives you the last two but no deduction on the way in.

A possible fourth break

Contributions made through payroll at work usually also skip Social Security and Medicare tax, the 7.65% FICA payroll tax. Contributions you make yourself outside payroll get the income tax deduction but not the FICA saving.

A worked example

Say you put $1,000 into your HSA through payroll, and your federal tax bracket is 22%.

Tax avoided	Amount
Federal income tax (22%)	$220
FICA payroll tax (7.65%)	$76.50
Total	$296.50

So $1,000 lands in the account for roughly $703.50 less in take-home pay, before counting any state income tax saving. If that $1,000 is later spent on a qualified medical bill, it's never taxed at all.

Who can open one

You need to be covered by a qualifying HDHP. The IRS sets the minimum deductible and maximum out-of-pocket amounts a plan must meet, plus the yearly contribution limits, and these change each year, so check the IRS's current figures. Once you enroll in Medicare, you can't add new money, though you keep what's already there.

How it differs from an FSA

A Flexible Spending Account generally has to be used within the plan year or the money is lost. An HSA doesn't: unspent money rolls over every year without limit. The account is also yours, not your employer's, so it comes with you when you change jobs.

The long game

Many people use their HSA like a checking account for this year's doctor visits. That captures the first tax break but wastes the second. If you can afford to pay current medical bills from other money, the balance can be invested and left to grow untaxed for decades.

That works because there's no deadline for reimbursing yourself. A medical bill you paid out of pocket after opening the HSA can be reimbursed years later, as long as you keep the receipt.

Rules on non-medical withdrawals

Before age 65, money taken out for anything other than qualified medical expenses is taxed as income and hit with a 20% penalty. After 65, the penalty goes away: non-medical withdrawals are taxed as ordinary income, much like a traditional IRA, while medical withdrawals stay tax-free at any age.

Learn it properly

Finance Brain's Health Savings Accounts lesson, in the Retirement Accounts and Tax-Advantaged Savings course, goes further into eligibility rules, the Medicare and Social Security timing trap, and using an HSA alongside other retirement accounts. It ends with a short quiz.

Finance Brain is educational content, not financial or tax advice. This post describes US rules.