Indiana HSA Tax Rules: All 92 Counties, One Shared Tax Base
Indiana is one of only a few states where every single county levies its own income tax on top of the state rate -- all 92 of them. That could easily mean 92 separate questions about HSA treatment. It doesn't, for the same structural reason it doesn't in Maryland.
Key takeaways
- Indiana's tax calculation starts from federal adjusted gross income -- already net of the HSA deduction -- then applies specific, listed additions and subtractions.
- All 92 Indiana counties levy their own income tax, but it's calculated on that same Indiana adjusted gross income, not an independently determined base.
- Because the county tax is derived from the same already-adjusted figure, it can't diverge from the state's HSA treatment -- structurally, not just as a matter of policy.
State level: starts from federal AGI
Indiana's own administrative code defines Indiana Adjusted Gross Income as starting with federal adjusted gross income, then applying specific required additions and subtractions. The HSA deduction is already reflected in federal AGI by the time Indiana's calculation begins, and it isn't one of the items Indiana requires adding back. Indiana then applies its flat state rate (currently near 3%) to that adjusted figure.
92 counties, one shared calculation
Indiana is unusual in that all 92 counties levy a county income tax (structured as either a County Adjusted Gross Income Tax or County Option Income Tax, depending on the county). Rates vary widely -- from about 0.50% in Ohio County up past 3% in the highest counties. But the key structural fact: county tax is calculated on the same Indiana adjusted gross income already used for the state tax, not a separately determined figure the way Ohio's individual municipalities or New York City's local tax are. Since that base already reflects the HSA exclusion, every one of Indiana's 92 counties automatically follows the same treatment -- there's no county-by-county variation to check.
Which county's rate applies
Your county tax rate is determined by where you lived on January 1 of the tax year, not where you work. Someone who lives in one county and commutes to a job in another still pays their home county's rate -- the same residence-based principle covered in our Maryland guide.
Sources: Indiana Department of Revenue; 45 IAC 3.1 (Indiana Adjusted Gross Income Tax administrative code); IRS Publication 969 for federal HSA treatment.