North Carolina requires UIM equal to UM, pays it from the first dollar beyond the other driver's coverage, and lets limits from separate policies add
North Carolina's rules are in G.S. 20-279.21 (UM, UIM and stacking) and the liability minimums in G.S. 20-279.5. The injury deadline is in G.S. 1-52 and the extension for minors in G.S. 1-17.
Read how stacked and single-limit coverage differ in North Carolina, check what section 20-279.21 says, or see how North Carolina UM and UIM work.