The Complete HSA Guide

A Health Savings Account (HSA) is a tax-advantaged savings and investment account designed for people enrolled in a High-Deductible Health Plan (HDHP). Created by the Medicare Modernization Act of 2003, the HSA was intended to help Americans save for medical expenses. But its unique triple tax advantage has made it one of the most powerful wealth-building tools available to anyone who qualifies.

Here is how it works: you contribute pre-tax dollars (or tax-deductible after-tax dollars) into the account. The money sits in a cash balance or can be invested in stocks, bonds, ETFs, and mutual funds — just like an IRA. When you need to pay for a qualified medical expense, you withdraw the money tax-free. Unlike a Flexible Spending Account (FSA), your HSA balance rolls over year after year. There is no use-it-or-lose-it deadline. The money is yours, permanently.

The critical insight that most people miss: you are not required to use your HSA to pay for current medical expenses. You can pay medical bills out of pocket, keep your receipts, and let your HSA grow for years or decades. Then reimburse yourself tax-free at any point in the future. There is no time limit on reimbursement. This transforms the HSA from a simple medical spending account into a powerful long-term investment vehicle.

These limits include both your contributions and any employer contributions. If your employer contributes $1,000 to your HSA, your personal contribution limit for self-only coverage drops to $3,300. The catch-up contribution of $1,000 is available to anyone age 55 or older by the end of the tax year. Unlike IRA and 401(k) catch-up provisions, the HSA catch-up amount has remained at $1,000 since HSAs were created (it is not indexed for inflation).

If you become HSA-eligible mid-year, you can either prorate your contribution (1/12 of the annual limit for each month of eligibility) or use the last-month rule: if you are eligible on December 1, you can contribute the full annual amount. However, you must remain HSA-eligible for the entire following year (the “testing period”), or the excess contribution becomes taxable and subject to a 10% penalty.

You have until the tax filing deadline (typically April 15) to make HSA contributions for the prior tax year, similar to IRA contributions. This gives you extra time to maximize your contribution if you did not hit the limit during the calendar year.

Here is the strategy that financial planners call the “stealth IRA” — and it is the single most powerful reason to have an HSA even if you are healthy and rarely visit the doctor.

The key insight: the IRS does not require you to reimburse medical expenses in the same year they occur. There is no time limit. You can pay for a doctor visit out of pocket in 2025, save the receipt, and reimburse yourself from your HSA in 2055 — completely tax-free. The money grows tax-free in the meantime.

Most people treat their HSA like a checking account — they contribute money and spend it on copays and prescriptions. This is a massive missed opportunity. Only about 13% of HSA holders invest any portion of their balance, according to the Employee Benefit Research Institute. The other 87% are leaving the most powerful tax advantage in the country on the table.

If you are following the stealth IRA strategy above, you want to invest as aggressively as your time horizon allows. For someone in their 20s or 30s with decades until retirement, that means 100% equities — a total stock market index fund or S&P 500 index fund. The tax-free growth is the entire point. Keeping it in cash earning 0.01% APY defeats the purpose.

Most HSA providers require you to maintain a minimum cash balance (typically $1,000-$2,000) before you can invest the excess. Once you clear that threshold, you can allocate the rest to index funds, target-date funds, or individual stocks depending on the provider. Fidelity is the exception — they have no minimum cash requirement and let you invest every dollar from day one.