26 CFR 301.6363-3: -3 Transition years.

The State may by law provide for the transition to or from a qualified tax to the extent necessary to prevent double taxation or other unintended hardships, or to prevent unintended benefits, under State law. Generally, such provisions shall be administered by the State; but, if requested to do so by the Governor of the State, the Secretary or his delegate may in his discretion, agree to administer such provisions either solely or jointly with the State.