HSA-Eligible Health Plans: How the Triple Tax Advantage Works, With the Math

A health savings account (HSA) is a tax-advantaged account paired with an HSA-eligible health plan. It's built for medical expenses, but its tax treatment makes it useful for long-term saving too. Used carefully, it can outperform other account types for health costs in retirement.

The short version

• To contribute, you generally need coverage under an HSA-eligible health plan, no disqualifying other coverage, not be enrolled in Medicare, and not be claimed as someone's dependent.
• HSAs offer three tax benefits: contributions are deductible or pre-tax, growth is tax-free, and withdrawals for qualified medical expenses are tax-free.
• Payroll contributions through an employer generally also avoid Social Security and Medicare payroll taxes.
• Non-medical withdrawals before 65 owe income tax plus a 20% additional tax. After 65, they owe income tax only, similar to a traditional IRA.
• The money rolls over year to year and stays yours if you change jobs or plans.
• Annual contribution limits are set by the IRS and adjusted for inflation.

The three tax advantages

The math: HSA vs. a taxable account

A hypothetical saver contributes $4,000 of pre-tax income a year for 20 years, invested at 6%. They're in a 22% income tax bracket.

• HSA: the full $4,000 goes in each year; growth isn't taxed; withdrawals for medical costs are tax-free.
• Taxable account: income tax takes 22% first, leaving $3,120 to invest each year, and taxes on dividends and gains reduce the return. We approximate that as earning 5.1% after taxes.

The HSA ends up about 42% larger in this example, before counting payroll tax savings on contributions made through an employer.

The "save receipts" strategy

Some people pay current medical costs out of pocket, let the HSA grow invested, and keep receipts. Qualified expenses incurred after the HSA was established can generally be reimbursed tax-free later, even years later. This requires careful records and enough cash flow to pay medical bills now.

Choosing an HSA-eligible plan

HSA-eligible plans have higher deductibles, so the decision should start with total cost. Employer HSA contributions can change which plan is cheaper; see comparing health plans by total cost.

Things to watch

• Medicare ends contribution eligibility. Enrolling in any part of Medicare, including premium-free Part A, generally stops HSA contributions. Part A can be retroactive up to six months when you enroll after 65. See Medicare and employer coverage.
• Qualified expenses are defined by IRS rules. Keep documentation.
• Fees and investment options vary widely between HSA providers. You can generally transfer an HSA to another provider.
• State taxes: a few states don't follow the federal tax treatment of HSAs.
• Beneficiaries: a spouse can inherit an HSA as their own; other beneficiaries generally owe tax on the balance.

The takeaway

An HSA combines a pre-tax contribution, tax-free growth, and tax-free medical withdrawals, a combination no other account offers. If you're eligible and can afford the plan's deductible, contributing and investing the balance can build a dedicated, highly tax-efficient fund for future health costs.