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N430 Remark Code: Procedure Code Inconsistent With Units

N430 means the procedure code is inconsistent with the number of units billed. The units on the line do not make sense for how that code is defined, for example several units on a code meant to be reported once, or units that do not match a time or dosage definition.

Quick facts

Code
N430 (RARC N430)
Status
Active In use since November 5, 2007.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The line was denied or reduced because of a billing error the provider can correct. The patient should not be billed for the difference.
Official description
Procedure code is inconsistent with the units billed.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N430 means

Each procedure or HCPCS code has a unit definition. Some are “per session” or “per day” and should appear with one unit; some are time-based, such as each 15 minutes; drug codes use a dose defined in the code descriptor. N430 says the units reported on the line do not fit the code’s definition. The payer usually pairs it with CARC 16 or CARC 151.

Common causes

  • Per-encounter codes billed with more than one unit, often because a charge was entered once per body area or per test instead of once per session.
  • Time converted incorrectly. Minutes were entered as units, or rounding rules for timed codes were not applied.
  • Drug unit errors. The number of units billed did not match the HCPCS dose increment for the amount given, for example billing milligrams instead of the code’s unit size.
  • Bilateral services reported with two units when the payer expects one unit with a bilateral modifier, or the reverse.
  • Wrong code selected, so the units were right for the intended service but not for the billed code.

How to fix it

  1. Read the code definition for how units are counted, including any “each additional” or time increment language.
  2. Recalculate from the documentation: minutes, dose given, number of sites or sessions.
  3. Apply payer rules for bilateral reporting, timed-code rounding, and drug waste, which differ between payers.
  4. Send a corrected claim in CMS-1500 box 22 with resubmission code 7 and the original claim number, with the fixed units in box 24G.
  5. If the units were right, appeal with the documentation and a short explanation of how units were counted.

How to prevent it

Build unit logic into your charge master: default to one unit for per-session codes and convert drug doses using the code’s increment. For daily unit caps specifically, see MUE denials and units of service. Claims Validator can catch units that do not fit a code before the claim is submitted.

Codes that may appear with N430

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim has a billing error; N430 identifies it as a code-to-units mismatch.
  • CO-151 (Payment adjusted because the payer deems the information submitted does not support this many/frequency of services.): The payer does not consider the number of services supported.
  • CO-4 (The procedure code is inconsistent with the modifier used.): Can appear when a modifier that would explain multiple units is missing or incompatible with the code.
  • M53 (Missing/incomplete/invalid days or units of service.): Days or units of service are missing, incomplete, or invalid, a data problem rather than an inconsistency with the code.
  • N362 (The number of Days or Units of Service exceeds our acceptable maximum.): The units exceed the payer's acceptable maximum.
  • N203 (Missing/incomplete/invalid anesthesia time/units.): Anesthesia time or units are missing, incomplete, or invalid.

N430 FAQ

Where are units reported?

In CMS-1500 box 24G for each service line, and in the corresponding service line quantity on electronic claims. Institutional claims report units per revenue code line.

How is N430 different from an MUE denial?

An MUE edit caps units per day at a maximum. N430 is broader: it says the units simply do not fit the code, which can include cases below any maximum, like fractional or mismatched drug units.

Should I split the units across lines with a modifier?

Only when the payer's rules allow it and the documentation supports separate services. Splitting lines to get around an edit without support can create compliance problems.