CO-15 Denial Code: Authorization Number Missing or Invalid
The CO-15 denial code means an authorization was required and the number submitted on the claim is missing, wrong, or does not cover the service, provider, or dates billed. Unlike CO-197 (no authorization obtained at all), CO-15 usually means an authorization exists somewhere - it just was not transmitted correctly or does not line up with what was billed.
Common Causes
- The authorization number was left off the claim or entered with a typo
- The claim's dates of service fall outside the authorized date range
- The authorization was issued for a different CPT code, provider, or facility than what was billed
- The number of authorized units or visits was exhausted before this claim's date of service
- The authorization is on file with a different payer entity (for example, a carve-out vendor for behavioral health or imaging)
How to Fix CO-15
- Look up the authorization in the payer portal and compare its number, date range, CPT codes, units, and authorized provider against the claim
- If the number was missing or mistyped, add the correct authorization number and resubmit
- If the service date or code differs from what was authorized, request an authorization update or retro-authorization from the payer before resubmitting
- If units were exhausted, determine whether additional units can be authorized retroactively; some payers allow this with clinical documentation
- Document every authorization in the encounter record at scheduling so the number flows onto the claim automatically
Frequently Asked Questions
CO-15 means the authorization number is missing, invalid, or does not apply to the billed service or provider. An authorization usually exists but does not match the claim - wrong number, wrong dates, wrong code, or exhausted units.
CO-197 means the required precertification or authorization was never obtained or is absent entirely. CO-15 means an authorization number was expected or submitted but is invalid or does not match the service billed. CO-15 is usually fixable by correcting the number or aligning the authorization; CO-197 often requires a retro-authorization request or appeal.
Pull the authorization from the payer portal, verify the number, valid dates, authorized CPT codes, units, and provider, correct whatever does not match the claim, and resubmit. If the service changed after authorization, ask the payer for an updated or retroactive authorization.
Related Denial Codes
Related Resources
Claim adjustment reason codes and remittance advice remark codes are standardized code sets maintained by X12. The explanations on this page are written in our own words for educational purposes, based on public CMS and Medicare contractor documentation. Payer policies vary - always confirm handling with the specific payer's guidance and your contracts.