<prompt> Human: We were checking our 2017 tax prep by accountant and noticed state tax was higher. We told accountant and the tax prep was redone without any explanation. Those taxes were filed.Now, from taxes filed by the same accountant, we got a notice from the state saying we underpaid on 2015 state tax, and there was interest on the bill. I asked him what the deal is with this. Accountant says its because state gross was more than federal. Also no other explanation.I recall we also got an underpayment notice maybe in 2016, but could have been for federal as a small amount of unreported income. I cannot confirm for what, just that it was an underpayment thing.I work in one state and live in another. My spouse works and lives in the same state. We live together. What do people think is going on? I never had this happen. But we also just started filing jointly in 2015. Same year I got accountant. But they filed 2014 for me on my own.UPDATE: Thanks for responses. Accountant says there is a discrepancy between states and my transportation as a write off not counting in my home state. I never had this come up before but I have no choice but to trust accountant. Similar responses support why this happened. Thank you  <response>: Some states dont count contributions to things like HSAs as tax deductible, while the IRS does.California, for example, has a publication pdf warning that shows the difference between California state tax law and federal tax law. 