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N670 Remark Code: Primary Procedure Under MPPR

N670 means the payer identified this service as the primary procedure for the Medicare Multiple Procedure Payment Reduction (MPPR) rule. The primary procedure is normally paid at its full rate, while the other procedures in the group are reduced.

Quick facts

Code
N670 (RARC N670)
Status
Active In use since July 15, 2013.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): Any reduction applied under MPPR is a contractual or program write-off and is not billed to the patient.
  • PR (Patient Responsibility): Deductible and coinsurance on the allowed amount are reported under PR.
Official description
This service code has been identified as the primary procedure code subject to the Medicare Multiple Procedure Payment Reduction (MPPR) rule.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N670 means

When several procedures in the same category are done in one session, some of the work, such as preparation, practice expense, or setup, overlaps. Medicare’s Multiple Procedure Payment Reduction accounts for that by paying the highest-valued procedure in full and reducing the payment for the others.

N670 is attached to the line the payer ranked first. It is the counterpart of N936, which marks the reduced secondary and tertiary procedures. By itself, N670 usually means this line received full payment, not a cut.

Why it matters

The ranking decides which line gets full payment. If the payer ranked the wrong procedure as primary, a higher-valued service may have been reduced. That can happen when:

  • A modifier on one line changed its value, for example professional or technical component modifiers.
  • Procedures were split across two claims, so the payer ranked each claim separately or ranked them differently from how you expected.
  • Units or modifiers were reported incorrectly, distorting the values.
  • The payer’s indicator for a code doesn’t match Medicare’s, so a service was pulled into or left out of the rule.

What to do

  1. List all procedures from that session with their allowed amounts and check which one the payer paid at full value.
  2. Confirm the ranking matches the highest-valued procedure under the payer’s schedule.
  3. Correct modifiers or units in box 24D and box 24G with a corrected claim, using resubmission code 7, if your data caused the misranking.
  4. Request reprocessing if the payer ranked incorrectly despite correct claim data.

How to prevent it

Bill procedures from the same session together on one claim, and review modifier usage for multi-procedure encounters. An ERA Analyzer that compares expected and paid amounts line by line makes misranked procedures stand out.

Codes that may appear with N670

  • CO-59 (Processed based on multiple or concurrent procedure rules. (For example multiple surgery or diagnostic imaging, concurrent anesthesia.)): Processed based on multiple or concurrent procedure rules.
  • CO-45 (Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.): The charge exceeded the allowed amount for the primary procedure.
  • N936 (This service code has been identified as the secondary or tertiary procedure code subject to the Medicare Multiple Procedure Payment Reduction…): Marks the secondary or tertiary procedures that receive the reduction.
  • N644 (Reimbursement has been made according to the bilateral procedure rule.): Pricing under the bilateral procedure rule.
  • N669 (Adjusted based on the Medicare fee schedule.): Pricing based on the Medicare fee schedule.

N670 FAQ

Which services does MPPR apply to?

Medicare applies multiple procedure reductions to certain groups of services, including some surgical, diagnostic imaging, therapy, and diagnostic testing services, with rules that differ by category. Check the payer's indicators for each code.

How does the payer pick the primary procedure?

Generally it ranks the procedures by their fee schedule value and treats the highest-valued one as primary, not necessarily the first line on the claim.

Do non-Medicare payers use MPPR?

Many commercial, Medicaid, and workers' compensation payers use similar multiple procedure rules, sometimes following Medicare's approach and sometimes their own percentages.