One or more of {Medicare, Medicaid, TRICARE, CHAMPVA, Group, Other, VA, IHS} checked — the program this claim is billed to. Dental claims typically check "Other" or "Group."
Two programs checked at once, which most clearinghouses reject. Medicare is checked for a routine adult cleaning that Medicare excludes (MBM Ch. 15 §150). The whole row is left blank when Box 11 already names an active policy.