[Mouton]

why couldn’t a state require an individual attending a meeting in their state to file a state tax return for the income they earned while attending? Or, suppose you’re on paid leave and you spend time in a state, why couldn’t a state require you to file a return for that income?

Actually it already is happening. My wife who works in Florida went to a training course in Minn where her company is headquartered. She got a tax bill for her time in that state. I went balistic but that seems to be the norm these days and fighting them over what is basically a few dollars is not economically worth it.

[Alberta's Child]

States have always had the legal authority to do exactly what you've said here. The problem was always in enforcement, and that the cost of collecting the taxes exceeded the tax revenue the state would get in most cases.

In your wife's case, it might be worth your while to have her check with the company's HR office to see how the state of Minnesota even knew about her attendance at the training course. I don't see how they would know that unless the company turned over your wife's name, address and maybe even her Social Security number to the Minnesota authorities.