How to Work CO-151 for Blue Cross Blue Shield

CO-151 is a CARC indicating that the payer has identified the claim as a duplicate of a previously submitted claim. The payer will not process the duplicate claim because the service has already been billed, paid, or is pending adjudication.

Duplicate claim denials occur when: (1) the same claim was submitted twice (electronic + paper, or retransmitted), (2) a corrected claim was submitted without indicating it was a replacement, (3) the same service was billed on multiple claim lines or claims, (4) the payer's system identified overlapping dates of service, or (5) the billing system automatically resubmitted a claim that appeared to have no response.

• 1Claim submitted to both local and home BCBS plans
• 2Corrected claim without frequency code 7
• 3Duplicate electronic submission
• 4Same service billed on multiple claims

• Original claim submission confirmation or trace number
• ERA/EOB from the original claim (showing it was processed or denied)
• Corrected claim form with frequency code 7 (if submitting a replacement)
• Payer correspondence regarding the original claim
• Billing system audit trail showing submission history

1. 1Check the ERA/EOB for the accompanying RARC code — it may specify what the claim duplicates.
2. 2Search your billing system for the original claim by claim number, date of service, and patient.
3. 3Verify whether the original claim was paid, denied, or is still pending.
4. 4Check if a corrected claim was submitted without the proper frequency code (7 for replacement).
5. 5Review the billing system for duplicate submission triggers (auto-resubmission, etc.).
6. 6Determine if the duplicate is legitimate (same service billed twice) or a system error.

1. 1If the original claim was paid: write off the CO-151 as a legitimate duplicate.
2. 2If the original claim was denied and you submitted a corrected claim: verify the corrected claim had frequency code 7. If not, resubmit with the correct frequency code.
3. 3If the claim is still pending: wait for the original claim to process. Do not resubmit.
4. 4If the duplicate was a system error: submit an appeal with proof of only one claim being intended.
5. 5If the claim was accidentally submitted twice: wait for the original to process, then appeal if needed.

CO-151 appeals are only necessary when the claim is not actually a duplicate — i.e., you only submitted one claim and the payer erroneously identified it as a duplicate. If the claim is a genuine duplicate (submitted twice), do not appeal. If you submitted a corrected claim and it was processed as a duplicate instead of a replacement, verify the frequency code and resubmit or appeal with the corrected claim documentation.

• Train staff on correct claim frequency codes (7 = replacement, 8 = void).
• Implement system controls to prevent duplicate electronic submissions.
• Set claim follow-up timers to avoid premature resubmission (wait 30+ days before following up).
• Never submit a paper claim if an electronic claim was already submitted for the same service.
• Audit billing system auto-resubmission features to ensure they don't create duplicates.
• Track claim status in the payer portal before resubmitting.
• Maintain a claim log to track submissions, corrections, and payment status.