CO-18: Exact duplicate claim or service

What causes it

• The claim was resubmitted instead of being corrected
• The clearinghouse sent it twice
• A legitimate repeat service on the same day was billed without a repeat modifier
• Somebody rebilled because the original showed no payment, when the original was actually still in process

How to work it

1. Find the original claim and check its status before doing anything else — most CO-18 work is wasted because the original was fine
2. If a genuine repeat service was performed, resubmit with the appropriate modifier, 76 or 77, and documentation of the repeat
3. If the original was denied and you are resubmitting the fix, send it as a corrected claim with the original claim number, not as a fresh claim

How to stop it recurring

A queue that rebills on a timer rather than on a status check generates these constantly, and each one buries the original.

Codes worked the same way

CO-18 is checked against the contract before any work is done. So are these, which is why a queue sorted by recovery route moves faster than one sorted by code number — the same person, in the same system, with the same evidence to hand, clears all of them in one pass.

• CO-45 — Charge exceeds the fee schedule
• CO-97 — Payment included in another service
• CO-288 — Referral absent
• PR-204 — Not covered by this plan
• OA-23 — Prior payer already adjudicated
• CO-286 — Appeal filed too late

Specialties that name this among their costliest

These are specialties whose own worst denials include one of this kind. The line under each is the denial they name, quoted from their page so you can see what the link is based on.

• Anesthesia
  Post-op pain blocks bundled into the anesthesia claim
• Ophthalmology
  Retinal imaging and fundus photography done at the same visit, with one line denied as bundled because the record never gives a separate reason for each test.
• Otolaryngology
  The operative note does not state which sinuses were entered on which side, so the sinus surgery lines are bundled together or only one side is allowed.
• Urgent Care
  A global urgent care case rate billed alongside a separate evaluation and management line where the contract pays one or the other, and the second line drops off
• Primary Care
  A preventive visit and a same-day problem visit written up in one undivided note, so the problem visit bundles into the wellness visit and is not paid separately.
• Oncology
  Payer required the drug through its contracted specialty pharmacy, the practice infused from its own stock, and the buy-and-bill claim was denied in full.

What leaving it costs

Working a denied claim costs $57.23 per denied claim in administrative time. Source. At 100 denials a month — an illustration, not a measurement of your practice — that is $5,723 a month, or $68,676 a year, in labour alone.

The figure that makes it worth spending: about 90% of initially denied claims are eventually paid. Source. The reason a denial sits is almost never that nobody knows how to work it — it is that nobody has the hours.

Questions

Code descriptions are the standard X12 claim adjustment reason and remittance advice remark code text. Payer policies differ, and the payer’s own coverage policy governs any individual claim. This page is working guidance, not legal or clinical advice.