Question: Answer: A private payer could have a black box edit. You would need to check with a rep for a recommendation. Watch out: You can find Medicare's other allowed modifiers for any given CPT code in the Medicare Physician Fee Schedule (MPFS). Columns Y-AC indicate if modifier 51 (Multiple procedure), 50 (Bilateral procedure), etc. apply. To determine which code receives modifier 51, you need to know the code's relative value units, which are also listed in the MPFS. Private payers may not adjust claim items in descending order as Medicare's Outpatient Code Editor software does. If you append modifier 51 to a higher valued item, the private payer may apply the adjustment based on your coding, costing you payment. You should instead list the items in descending relative value order from highest to lowest. Append modifier 51 to the lower priced procedure as necessary. The insurer will then apply the typical 50 percent, multiple procedure reduction to the lower priced code.