What Are Denial Codes? Understanding CARC and RARC

When a payer doesn't pay a claim in full, it doesn't just say "no" — it tells you why, in code. Those are denial codes, and learning to read them is one of the most useful skills in billing. They point straight to the reason a claim was denied or adjusted, which is the first step to fixing it. Here's the plain-English guide.

What are denial codes?

Denial codes are standardized codes that insurance payers use to explain why a claim — or part of a claim — wasn't paid the way it was billed. They appear on the EOB (Explanation of Benefits) or ERA (Electronic Remittance Advice) that comes back after a claim is processed.

Instead of writing out a full explanation, payers use these standardized codes so the reason is consistent and machine-readable. Read them correctly, and you know exactly why the money didn't come through.

CARC vs RARC

There are two main types, and they work together:

• CARC (Claim Adjustment Reason Codes) — explain why an adjustment or denial happened. This is the main reason: not covered, exceeds the fee schedule, bundled, and so on.
• RARC (Remittance Advice Remark Codes) — provide extra detail that supplements the CARC. They add context or specifics the reason code alone doesn't fully cover.

Think of the CARC as the headline reason and the RARC as the footnote that explains more. Read together, they give the full picture of what happened with the claim.

Common examples

A few codes come up constantly (these are widely used standardized codes):

• CO-97 — the service is bundled into another service that was already paid.
• CO-45 — the charge exceeds the payer's fee schedule or allowed amount.
• CO-16 — the claim is missing information or has an error.
• PR-204 — the service isn't covered under the patient's plan.

("CO" and "PR" prefixes indicate who's responsible for the adjustment — for example, a contractual obligation vs patient responsibility.) Recognizing common codes lets billing staff quickly understand and act on a denial.

Why they matter

Denial codes matter because they tell you exactly what to do next. A denial without a reason is a mystery; a denial with a code is a to-do list:

• The code tells you why it was denied.
• That tells you whether it's fixable, and how.
• It tells you whether to correct and resubmit, or appeal.
• And across many claims, the codes reveal patterns — the same code appearing over and over points to a root cause worth fixing.

Without reading the codes, denials just pile up. With them, each denial becomes a solvable problem.

How to use them

The practical workflow:

1. Read the code on the EOB/ERA.
2. Understand the reason it represents (CARC + any RARC).
3. Act — correct and resubmit if it's fixable, or appeal if it's recoverable.
4. Spot patterns — track which codes recur, and fix the upstream cause so the same denial stops happening.

Why it matters

Denial codes are the key to turning denials from lost revenue into recovered revenue. They tell you precisely why each claim wasn't paid and what to do about it — and, tracked over time, they reveal the recurring problems quietly costing the practice money. Reading and acting on them is the heart of effective denial management.

Where AlphaTek fits

At AlphaTek Solutions, reading denial codes, working the denials they explain, and fixing the patterns behind them is core to our denial management work. If denials are piling up unworked, talk to us.