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N122 Remark Code: Add-On Code Billed Without Primary

N122 means an add-on code was billed by itself. Add-on codes describe work done in addition to a primary procedure and are only payable when that primary procedure is reported on the same claim, or otherwise recognized by the payer, for the same date and provider.

Quick facts

Code
N122 (RARC N122)
Status
Active In use since September 12, 2002; last modified August 1, 2005.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): A coding denial. The provider should not bill the patient; correct the claim so the primary service is present.
Official description
Add-on code cannot be billed by itself.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N122 means

Add-on codes cover extra time, extra units, or additional components of a primary procedure. They never stand alone. N122 tells you the payer looked for an eligible primary procedure with the add-on and did not find one.

It often appears with CARC 107, which describes a missing qualifying service, or CARC B15.

Common causes

  • The primary procedure line was dropped during charge entry or split onto a separate claim.
  • The primary was performed by a different provider, and the add-on was billed under the second provider alone.
  • The add-on was reported with a primary code that is not one of its approved primaries.
  • The primary line had a different date of service than the add-on because of a keying error.
  • The primary was denied, leaving the add-on without support.

How to fix it

  1. Look for the primary procedure in the encounter: was it performed, by whom, and on what date?
  2. Check the pairing against the payer’s list of eligible primary codes for the add-on.
  3. Rebuild the claim with the primary and add-on on separate lines in CMS-1500 box 24D, matched dates in 24A, and the same rendering provider where required.
  4. Send a corrected claim with resubmission code 7 in box 22 and the original claim number. If the primary already paid on another claim, ask the payer how it wants the add-on submitted.

How to prevent it

Use a charge-entry rule that blocks add-on codes unless an approved primary is on the same encounter. Payer add-on edit lists can be loaded into pre-billing edits; Claims Validator can flag lone add-on lines before the claim leaves. For broader code-pair rules, see the NCCI bundling guide.

Codes that may appear with N122

  • CO-107 (The related or qualifying claim/service was not identified on this claim.): The related or qualifying claim or service was not identified on this claim.
  • CO-B15 (This service/procedure requires that a qualifying service/procedure be received and covered.): The service requires a qualifying service to be received and covered.
  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim has a billing error; N122 specifies the missing primary procedure.
  • N161 (This drug/service/supply is covered only when the associated service is covered.): A drug, service, or supply is covered only when the associated service is covered.
  • M51 (Missing/incomplete/invalid procedure code(s).): Flags a missing, incomplete, or invalid procedure code.
  • N390 (This service/report cannot be billed separately.): Says a service or report cannot be billed separately.

N122 FAQ

How do I know a code is an add-on?

Code sets mark add-on codes and describe them as used in addition to a primary procedure. Payer edits, including Medicare's add-on code edit files, also list which primary codes each add-on can accompany.

The primary procedure was denied. Will the add-on also deny?

Usually yes. If the primary line is denied, the add-on typically follows. Fix or appeal the primary line first.

Can the primary be on a different claim?

Some payers can match across claims for the same date and provider, but many cannot. Billing the primary and add-on together on one claim avoids N122.