Previously paid
The payer already paid for this service on an earlier claim.
CO = Contractual Obligation. The provider owes the difference. The patient cannot be billed for this amount. The same reason code can appear with a different group code; the group decides who may be billed.
Usual causes
- Duplicate submission after the first claim paid.
- Another provider was paid for the same service (purchased tests, global surgery).
- Service bundled into a payment already made.
The fix
Find the earlier payment and post it. If a second, separate service was done, resubmit with the right modifier. If another provider was paid for your work, resolve it with that provider or appeal with proof you performed the service.
Appeal or corrected claim?
Usually nothing; resubmit with a modifier for a distinct service; appeal with proof when another provider was paid for your service.
Deadline to watch
Timely filing or appeal window.
Exact limits are in your payer contract or provider manual. When in doubt, send the correction or appeal this week.
CO-B13 in short
What does CO-B13 mean?
The payer already paid for this service on an earlier claim. The official X12 text reads: "Previously paid. Payment for this claim/service may have been provided in a previous payment."
What usually causes a CO-B13 denial?
Duplicate submission after the first claim paid. Another provider was paid for the same service (purchased tests, global surgery). Service bundled into a payment already made.
How do I fix CO-B13?
Find the earlier payment and post it. If a second, separate service was done, resubmit with the right modifier. If another provider was paid for your work, resolve it with that provider or appeal with proof you performed the service.
Should I appeal CO-B13 or send a corrected claim?
Nothing to send. Usually nothing; resubmit with a modifier for a distinct service; appeal with proof when another provider was paid for your service.
What deadline applies to CO-B13?
Timely filing or appeal window.