AGAR Guide
CARC18ReferenceCurrentVerified Aug 15, 2026

CARC 18

AR Guide workflow

Step-by-step: Duplicate Claims

✓ Workflow verified Aug 15, 2026 · Verified via review of official sources and AR Guide practice testing — not payer policy. View the full guide

  1. VerifySteps 1–9

    1. Original claim number and its status

    2. Date of service, charges and patient match

    3. Whether this was meant to be a corrected claim

    4. Replacement vs. new claim indicator used

    5. CARC 18 and the accompanying remark code

    6. Search for the prior claim using the same dates of service and charges

    7. Confirm whether the original claim was already paid

    8. Check whether this was meant to be a corrected or replacement claim

    9. Compare the duplicate to the original for any differences

  2. ActSteps 10–12

    1. If it is truly a duplicate, confirm the original was handled correctly — no appeal needed

    2. If it is a corrected claim, resubmit with the correct replacement indicator

    3. If the original was denied, appeal the original claim with the correct information

  3. Document & QASteps 13–18

    1. The original claim number and its status

    2. Payment or denial details for the original claim

    3. Evidence this was a corrected claim if applicable

    4. Use a claim scrubber that detects duplicates before submission

    5. Train staff on replacement vs. new claim submission

    6. Confirm the original claim's status before touching the duplicate

Check the original claim before touching the duplicate: Note

A duplicate denial means the payer already processed the service. If the original paid, there is nothing to do; if it was denied, appeal the original claim, not the duplicate.

If you take the wrong path: Appealing the duplicate instead of the original is rejected. Resubmitting a correction as a new claim (frequency 1) creates a second duplicate.

AR Guide explanation

What it means

The payer identified the claim as an exact duplicate of a claim/service already processed.

AR Guide knowledge

Common denial category

Duplicate Claims — The payer identified the claim as a duplicate of a previously processed claim. Verify the original before doing anything — this is often a no-action item.

AR Guide knowledge

Most common causes

  • Same claim submitted twice
  • Corrected claim sent as a new claim instead of a replacement
  • Duplicate line items on one claim

AR Guide knowledge

Action in your PM/EMR system

In your PM system: search the account for the prior claim by date of service and charge before touching the duplicate. If it was meant to be a correction, resubmit with frequency code 7 — never a new claim.

Illustrative scenario

Real-world example

A claim was denied with CARC 18 as an exact duplicate. The original had already paid, so the correct action was no action — resubmitting the duplicate would have been a second error.

Example — not a claim about any specific payer or account.

AR Guide knowledge

What AR should verify

  1. Search for the prior claim using the same dates of service and charges
  2. Confirm whether the original claim was already paid
  3. Check if this was meant to be a corrected/replacement claim

AR Guide knowledge

Recommended action

  1. If it is truly a duplicate, no appeal is needed — confirm the original was handled correctly
  2. If it is a corrected claim, resubmit with the correct replacement indicator

Appeal template

Duplicate Claim Appeal — Corrected Claim Was Legitimate

Appeal a duplicate denial where a legitimate corrected claim (frequency code 7) was treated as a new duplicate.

For: Billing staff appealing CARC 18 denials on corrected claims. · Last reviewed 2026-08-16

Download .doc template

Educational starting point — not legal advice. Customize every [bracketed] placeholder and verify the payer's appeal address and deadline from the payer's own documentation. All templates

AR Guide knowledge

QA checkpoint

  • Use a claim scrubber that detects duplicates before submission
  • Train staff on replacement vs. new claim submission

About this guidance: Note

AR Guide knowledge is general reference content written by our team — it is not payer-specific policy and never replaces the payer’s documentation or your contract. Always confirm specifics with the payer.

Priority 2

Commonly paired RARCs

RARCs commonly accompany CARC 18 on the ERA/EOB. Select the one on your line to focus the workflow, or use the list as a lookup.

  • RARCN111No appeal right except duplicate claim/service issue. This service was included in a claim that has been previously billed and adjudicated.Confirm the original claim's status. If the original paid, no action. If the original was denied, appeal that original claim instead of the duplicate.
  • RARCN522Duplicate of a claim processed, or to be processed, as a crossover claim.
  • RARCM86Service denied because payment already made for same/similar procedure within set time frame.

Priority 3

Payer-specific nuance

How major payers handle this denial — what AR Guide has verified, and what you must confirm with the payer. We never publish payer handling we have not verified.

Medicare

How each payer wants corrected or replacement claims submitted varies. If the 'duplicate' was actually a correction, follow the payer's corrected-claim rules rather than appealing the duplicate — confirm the corrected-claim process with the payer before resubmitting.

Medicaid

How each payer wants corrected or replacement claims submitted varies. If the 'duplicate' was actually a correction, follow the payer's corrected-claim rules rather than appealing the duplicate — confirm the corrected-claim process with the payer before resubmitting.

UnitedHealthcare

How each payer wants corrected or replacement claims submitted varies. If the 'duplicate' was actually a correction, follow the payer's corrected-claim rules rather than appealing the duplicate — confirm the corrected-claim process with the payer before resubmitting.

Aetna

How each payer wants corrected or replacement claims submitted varies. If the 'duplicate' was actually a correction, follow the payer's corrected-claim rules rather than appealing the duplicate — confirm the corrected-claim process with the payer before resubmitting.

Cigna

How each payer wants corrected or replacement claims submitted varies. If the 'duplicate' was actually a correction, follow the payer's corrected-claim rules rather than appealing the duplicate — confirm the corrected-claim process with the payer before resubmitting.

Anthem (BCBS)

How each payer wants corrected or replacement claims submitted varies. If the 'duplicate' was actually a correction, follow the payer's corrected-claim rules rather than appealing the duplicate — confirm the corrected-claim process with the payer before resubmitting.

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