By Ariele Doolittle (June 4, 2018, 4:28 PM EDT) -- As state tax lawyers, we are often asked for advice on navigating different — and often competing — state tax schemes. The law in this area is subject to a handful of constitutional limitations. For instance, the Commerce Clause requires (among other things) that state taxes be fairly apportioned.[1] So in the case of nonresidents and other out-of-state or multistate taxpayers, many state tax schemes determine the taxability of a transaction or person based on the numbers of days spent in the taxing state. Consequently, our advice to nonresident taxpayers often turns on the number of "days" involved. This concept of counting "days" is actually pretty important in our world! But one thing that can be interesting in these cases is seeing how different states treat seemingly similar situations or transactions....