Mississippi folds underinsured coverage into UM and has courts, not the statute, decide stacking
Mississippi's rules are in Miss. Code 83-11-101 (UM required and rejection), 83-11-103 (definitions, including underinsured vehicles) and 83-11-102 (the single-limit non-stacking option). Minimum limits are in 63-15-3, the deadline in 15-1-49 and the fault rule in 11-7-15.
Read how stacked and single-limit coverage differ in Mississippi, check what the statutes say and leave to the courts, or see how Mississippi UM covers underinsured drivers.