@grasshopper612 wrote:
my question was, how did they get away with not allowing it previously because of the rules about double taxation re: comptroller of Maryland v Wynne.
The Wynne case (decision) is somewhat complicated, particularly in one respect; offering a credit is only one method in which a state can comply with the decision.
Regardless, it is not unusual for states (as well as other governmental units) to either delay compliance or even fail to comply until forced to do so by subsequent litigation. For example, and without going into detail, one aspect of the Illinois trust residency scheme was held to be unconstitutional by an Illinois court of appeal well over five years ago yet the statute has never been changed and, apparently, is still enforced (at least the instructions for the Illinois return still adhere to the definition that was held to be unconstitutional in large part).
Irrespective of the nature of the decision, retroactive application can be limited by a number of factors, including a statute of limitations. In any event, good luck getting any reasonable response and/or action from the IL DOR.
