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CO-B16 Denial Code: New Patient Qualifications Not Met

CO-B16 means the payer determined that the patient did not meet the definition of a new patient, so a new patient visit code was denied. Usually the patient had been seen by the same physician, or one of the same specialty in the group, within the past three years.

Quick facts

Code
CO-B16 (CARC B16)
Status
Active In use since January 1, 1995; last modified September 30, 2007.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The provider absorbs the denied amount and should rebill with an established patient visit code.
Official description
'New Patient' qualifications were not met.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-B16 means

CARC B16 says “new patient” qualifications were not met. The claim used a new patient visit code, but the payer’s claims history shows the patient already received professional services from this physician, or from another physician of the same specialty in the same group, within the past three years.

New patient visits are generally valued higher than established patient visits, so payers check this closely. The definition most payers follow comes from the code set and Medicare guidance: a new patient hasn’t received any professional services from the physician, or another physician of the exact same specialty and subspecialty in the same group, in the prior three years.

Common causes

  • Patient seen by another same-specialty physician in the group within three years.
  • Patient returning after a gap of less than three years, for example after two and a half years.
  • Group merger or TIN change, where prior visits under the old group still count.
  • Previous non-visit services, such as a procedure or interpretation by the same physician, which can count as professional services.
  • Taxonomy on file doesn’t show a different specialty, so the payer treats two specialties as the same.
  • Front desk registers the patient as new in the system because the old chart wasn’t found.

How to fix it

  1. Check the patient’s history across all providers and locations in the group for the prior three years.
  2. If the patient was established, rebill with the right established patient code, supported by the documentation, and send a corrected claim with resubmission code 7 in box 22.
  3. If the prior service was by a different specialty, confirm each provider’s taxonomy with the payer and appeal with that information.
  4. If the payer’s history is wrong, for example it’s mixing up patients, request reprocessing with evidence.
  5. Don’t bill the patient for the denied amount.

How to prevent it

  • Search for prior visits across the whole group before booking a new patient visit.
  • Merge duplicate patient records so history isn’t missed.
  • Keep provider taxonomies accurate with each payer. See provider enrollment denials.
  • Flag new patient codes for patients with any history. A Claims Validator can catch new patient codes on patients with recent visits.

Specialty notes

Behavioral health groups with psychiatrists and psychiatric nurse practitioners should check how each payer defines specialty for this rule. Multi-specialty groups see CO-B16 when specialties aren’t clearly separated in payer enrollment.

Remark codes that may appear with CO-B16

  • N657 (This should be billed with the appropriate code for these services.): The service should be billed with the appropriate code, here an established patient visit.
  • M13 (Only one initial visit is covered per specialty per medical group.): Only one initial visit is covered per specialty per medical group.
  • CO-B14 (Only one visit or consultation per physician per day is covered.): Only one visit per physician per day is covered.
  • CO-150 (Payer deems the information submitted does not support this level of service.): Documentation doesn't support the level of service billed.
  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Missing or invalid claim information.
  • CO-4 (The procedure code is inconsistent with the modifier used.): Procedure inconsistent with the modifier used.

CO-B16 FAQ

Who counts as a new patient?

Under the standard definition used by Medicare and most payers, a new patient has not received any professional services from the physician, or another physician of the exact same specialty and subspecialty in the same group practice, within the past three years.

Does a new location make the patient new?

No. If the patient was seen within three years by the same physician or a same-specialty physician in the same group, they're established even at a different office.

What about a different specialty in the same group?

A patient seeing a physician of a different specialty or subspecialty in the group may qualify as new to that physician. The taxonomy on file must reflect the specialty for payers to recognize it.

How do I fix CO-B16?

Rebill the visit with the appropriate established patient code at the level the documentation supports, using resubmission code 7 in box 22.