I can't understand these posts about "I've filed in NC for many years and never saw a D-400 form, what is it?" This is equivalent to saying "I've filed in the US for many years and never saw a 1040 form, what is it? I have filed in NC for 41 years and ALWAYS had to file a D-400. Maybe the manner in which you submitted your taxes doesn't explicitly show the forms being used? But rest assured, visible or not, NC residents have always filed D-400 forms.
