I was once trying to figure out taxes owed on some RSUs granted in California that vested in North Carolina (and some other edge case that I can’t remember). Hoh boy. What a rabbit hole. I didn’t think the CPA that I hired to do my taxes handled it correctly, so I started digging into the tax laws and regulations. Couldn’t find anything that covered my specific case. So I started digging into court cases involving disputes over RSU taxes owed in North Carolina and found conflicting outcomes.
I brought what I had found back to the CPA who basically said something along the lines of: there is no absolute “rule” for what to do in this case like you’re looking for. We make a good faith effort to mirror what was done in similar prior situations, write a number down, and then forget about it unless you hear from the IRS.
Did not make me feel very confident about the legal system.