Commit five diagnosis codes to memory. All diagnosis codes were not created equal -- and if the ones you're listing for the primary diagnosis aren't on one Medicare intermediary's list, you won't get paid. Effective Nov. 1, physical and occupational therapy claims submitted to National Government Services must list one of the following V codes as the primary diagnosis to show the encounter's necessity, according to a revised local coverage decision (L26884): Each V code must be followed by secondary and subsequent diagnosis codes representing the specific condition requiring therapy services. Claims without a secondary diagnosis may be denied.