CO-170 means the payer will not pay this service from the provider type or specialty that billed it. Often the taxonomy code is wrong, the provider is enrolled under the wrong specialty, or the service must be billed by a different kind of provider. Check enrollment and the claim's provider details.
The official wording
The X12 Claim Adjustment Reason Code list defines 170 as: "Payment is denied when performed/billed by this type of provider."
The letters in front are the group code. CO means contractual obligation (the provider absorbs it), PR means patient responsibility, and OA is other adjustment. The same reason code can come with different group codes, so always read both.
Common causes
- The taxonomy code on the claim does not match the payer's enrollment record.
- The provider is enrolled under one specialty but billed a service only another specialty can bill.
- A mid-level provider billed a service the plan only pays to physicians, or the reverse.
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How to fix it
- Check the rendering provider's taxonomy and specialty on the claim and in the payer's enrollment.
- If enrollment is wrong, update it with the payer, then ask for reprocessing.
- If the service must be billed by another provider type, bill under the right provider if they actually performed or supervised it, following the payer's rules.
One claim sent under the wrong provider type
A nurse practitioner sees the patient. The claim lists the group's taxonomy as the rendering taxonomy and the payer has the NP enrolled under a different specialty.
| Item | On the claim | What it means |
|---|---|---|
| Rendering provider | NP, NPI on line 24J | Enrolled with the payer as Nurse Practitioner, Family |
| Taxonomy on claim | Group code (Internal Medicine) | Does not match the payer's record for this NPI |
| Remittance | CO-170 | Denied for this type of provider |
| Fix | Use the NP's own enrolled taxonomy | Send a corrected claim |
Some CO-170 denials are real benefit rules (the plan only pays certain provider types for that service). Others are just a taxonomy mismatch.
Common provider-type rules
If the taxonomy was right, the denial is probably one of these plan rules.
| Rule | Example | What to do |
|---|---|---|
| Only physicians can bill it | Certain interpretations or procedures | Have the physician perform and bill it, or check incident-to rules |
| Specialty not enrolled | Behavioral health billed by a provider enrolled as primary care | Update enrollment with the payer |
| Therapy assistants | PTA or COTA services billed without the right modifier | Use CQ/CO modifiers for Medicare and bill under the supervising therapist |
| Facility vs professional | A service billed on a 1500 that the plan pays only to facilities | Check where the plan wants it billed |
Taxonomy goes in box 24J shaded area / 2310B PRV for the rendering provider and 2000A PRV for billing.
How to fix CO-170
- Check the rendering provider's enrolled specialty and taxonomy with the payer (portal or provider services).
- Compare it with the taxonomy sent on the claim and NPPES.
- If the taxonomy was wrong, fix it and send a corrected claim.
- If the plan truly does not pay this provider type for the service, write it off or bill under the right provider next time.
- If the enrollment record is wrong, ask the payer to update it, then reprocess.
CO-170 checklist
- ☐ Each provider's taxonomy matches NPPES and the payer enrollment.
- ☐ Rendering and billing taxonomy are sent in the right loops.
- ☐ Mid-level services checked against the payer's provider-type rules.
- ☐ Enrollment updated when a provider's specialty changes.
Questions people ask about CO-170
Can I bill the patient for CO-170?
No.
Can CO-170 come from a wrong taxonomy code?
Yes. A taxonomy on the claim that does not match the payer's enrollment is one of the most common causes.
Where do I find the taxonomy on the claim?
Rendering provider: shaded box 24J or loop 2310B PRV. Billing provider: box 33 or loop 2000A PRV.
Can CO-170 be fixed with a corrected claim?
Yes, when the cause was a wrong taxonomy or provider. Not when the plan never pays that provider type.
Is CO-170 common for nurse practitioners?
Yes. Check each plan's rules for NPs and PAs, and whether incident-to billing is allowed.
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All denial code guides
PR-1 · PR-2 · PR-3 · CO-4 · CO-5 · CO-11 · CO-15 · CO-16 · OA-18 · CO-22 · OA-23 · CO-24 · CO-26 · CO-27 · CO-29 · CO-31 · CO-45 · CO-49 · CO-50 · CO-59 · PR-96 · CO-97 · CO-109 · CO-119 · CO-129 · CO-140 · CO-146 · CO-151 · CO-167 · CO-170 · CO-181 · CO-185 · CO-197 · CO-198 · PR-204 · CO-234 · CO-236 · CO-242 · CO-252 · CO-253 · CO-288 · CO-A1 · CO-B7 · MA130 · N130 · N23 · N290
Timely filing limits by payer: Cigna timely filing limit · HealthSpring timely filing limit · Aetna timely filing limit · UnitedHealthcare timely filing limit · Humana timely filing limit · corrected claim timely filing limits
Sources: X12 Claim Adjustment Reason Code list (170), read October 12, 2026; CMS Medicare guidance where Medicare rules are mentioned. Last reviewed October 12, 2026. General information, not coding or legal advice. Payer rules differ, so check the remark code and the payer's own policy.