An interesting thread is over in the Business Operations and Development sub-forum. Does Fed or State Law Prevail?
I don't know why it was created there, as it seems to belong here. Rather than bother the moderators to spend time moving the thread, I am starting a related thread here, and kicking it off with a good article that summarizes the current state (pun intended) of state tax issues in light of TCJA.
The Tax Cuts and Jobs Act: State tax considerations, impacts, and responses