Michigan HSA Tax Rules: A Rate That's Recalculated Every Year
Michigan conforms to federal HSA tax treatment, the same as most states. What's actually distinctive about Michigan is its rate itself -- not fixed by the legislature on a schedule, but recalculated every single year by a statutory formula, and it has genuinely changed before.
Key takeaways
- Michigan conforms to federal HSA tax treatment -- contributions, growth, and qualified withdrawals are all state-tax-free.
- Michigan's flat rate is recalculated annually by a statutory formula, not set on a multi-year legislated schedule -- it actually dropped to 4.05% for 2023 before reverting to 4.25%.
- The Michigan Department of Treasury reconfirmed the rate stays at 4.25% for the 2026 tax year, since the statutory trigger for a reduction wasn't met.
Full conformity, same as most states
Michigan follows federal HSA rules directly: contributions are deductible on your Michigan return, investment growth inside the account isn't state-taxed, and qualified withdrawals stay tax-free. This part of the picture is the same as most conforming states.
Why Michigan's rate isn't actually fixed
A 2015 Michigan law set up something different from a typical legislated phase-down: each year, after the state's Annual Comprehensive Financial Report is published, the state treasurer and legislative fiscal agencies run a required calculation comparing general fund revenue growth to inflation. If revenue growth exceeds inflation by enough, the rate drops. This isn't hypothetical -- it actually triggered a reduction to 4.05% for the 2023 tax year. Whether that reduction was permanent or a one-time event became a real point of dispute, and the rate reverted to 4.25% afterward, where it has stayed since -- the Michigan Department of Treasury's own April 2026 announcement confirms the formula was run again for the 2026 tax year and didn't produce a reduction.
A note on city-level tax, separate from HSA rules
Some Michigan cities, including Detroit, levy their own local income tax on top of the state rate -- typically 1% to 2.4% for residents. This is a genuinely separate question from HSA treatment, though: your HSA contribution's federal and state tax benefit doesn't change based on which Michigan city you live in.
Sources: Michigan Department of Treasury, 2026 individual income tax rate determination; IRS Publication 969 for federal HSA treatment.