Working Denials: A Step-by-Step Workflow

Not all denials are the same — and treating them as if they are is one of the most common reasons billing offices lose recoverable revenue.

Some denials should be corrected and resubmitted. Some need a formal appeal with clinical documentation. Some transfer cleanly to patient responsibility. Some are routine contractual adjustments that require nothing more than a write-off. And some need a phone call or portal check before you can even decide what to do next.

The key is to identify the denial reason quickly, choose the right action, and get it into your tracking system before the resubmission or appeal deadline passes. This guide walks through that workflow from start to finish.

Quick Reference

Table of Contents

1. What Is a Claim Denial?
2. Denial vs. Rejection: Why the Difference Matters
3. Start With the EOB or ERA
4. The Five-Question Denial Triage
5. Common Denial Categories and What to Do
6. Decide the Next Action
7. When to Correct and Resubmit
8. When to Appeal
9. What Every Appeal Packet Should Include
10. Track Every Denial
11. Common Denial Workflow Mistakes
12. Simple Daily Denial Workflow
13. Key Takeaways
14. Related Forms and Templates
15. Related Guides

What Is a Claim Denial?

A claim denial is a decision by a payer that a submitted claim — or a specific line on a claim — will not be paid. The payer communicates that decision through an EOB or ERA, along with a reason code explaining why.

But not every payment problem is a denial. Before you can work a claim correctly, it helps to know what you're actually looking at.

Understanding the difference matters because each one has a different workflow, a different deadline, and a different resolution path.

Denial vs. Rejection: Why the Difference Matters

A rejection happens before the payer ever adjudicates your claim. The clearinghouse or payer's front-end system returned it — usually because of a formatting error, a missing field, an eligibility mismatch, or an NPI issue. Rejections do not appear on an EOB. They show up in your clearinghouse rejection report or payer portal. They typically do not have formal appeal deadlines, and you can usually correct and resubmit immediately.

A denial happens after the payer receives and reviews the claim. It appears on an EOB or ERA with a CARC code. Denials may have appeal deadlines — sometimes as short as 30 days from the denial date, sometimes 90 to 180 days. Missing that deadline can mean losing the right to appeal entirely.

Start With the EOB or ERA

When a denial arrives — whether on a paper EOB or an electronic ERA — the first step is to gather the key information before you decide anything.

For every denied line, identify:

• Patient name and date of birth — confirm this is the right account
• Denial date — this is when your appeal or resubmission deadline clock starts
• Claim number — the payer's assigned number for this claim
• Date of service — the specific DOS for the denied line
• CPT or HCPCS code — the procedure or service that was denied
• CARC code — the primary reason for the denial
• RARC code — supplemental detail when present
• Amount at risk — the dollar amount being denied or adjusted
• Payer notes — any free-text explanations accompanying the code

Do not rely on the CARC code alone to tell the full story. Read the RARC and any payer remarks. Two claims denied with CO-50 (medical necessity) can require completely different documentation to appeal.

The Five-Question Denial Triage

Before taking any action on a denied claim, answer these five questions. They will tell you exactly what to do next.

1. What exactly was denied?

Is it the entire claim, or just one line? Is it the procedure code, the diagnosis code, the authorization, or the patient's eligibility?

2. Why was it denied?

Look at the CARC and RARC codes together. Look up any unfamiliar codes — definitions can change and payer-specific application varies. Do not assume.

3. Is the denial correct?

Was there actually a billing error, or did the payer make a mistake? A denial can be wrong. Verify before writing anything off.

4. What documentation or correction is needed?

Does this need a corrected claim, a signed appeal letter, clinical records, authorization proof, a primary EOB, or a modifier added?

5. What is the deadline?

Find the appeal or resubmission deadline before you do anything else. Log it. If you don't know the deadline, call the payer or check the provider portal before proceeding.

Common Denial Categories and What to Do

Decide the Next Action

Once you have identified what was denied and why, the resolution path usually falls into one of these categories:

• Correct and resubmit — There was a fixable billing error. Correct the claim and resubmit with the appropriate frequency code.
• Appeal — The denial appears incorrect, or the denial reason is something you can dispute with documentation.
• Send records or documentation — The payer needs additional information before they will adjudicate the claim. Submit what they've requested by their deadline.
• Bill secondary insurance — The primary EOB is in hand. The remaining balance should be submitted to the secondary payer before billing the patient.
• Transfer to patient responsibility — The denial confirms the patient owes this amount (copay, deductible, coinsurance). Post to patient account and generate a statement after verifying secondary coverage, payer rules, and practice policy.
• Post contractual write-off — The adjustment is a standard contractual reduction. Write it off. Do not bill the patient.
• Call payer or check portal — The denial is unclear, or you need to verify claim status, auth status, or deadline information before deciding.
• Write off after review — After review, the denial is valid, the deadline has passed, or the amount does not justify the cost of appeal. Write off with appropriate documentation and supervisor approval.

When to Correct and Resubmit

Correcting and resubmitting is appropriate when the denial was caused by a fixable error on the original claim — not a payer disagreement about medical necessity or coverage.

Common situations that call for correction and resubmission:

• Demographic or ID errors — wrong member ID, incorrect date of birth, name mismatch
• Missing or incorrect modifier — CO-4 denials often resolve with the right modifier added
• Missing authorization number — if auth was obtained but not included in Box 23
• Incorrect place of service — POS code didn't match where the service was rendered
• Wrong NPI — rendering, billing, or referring NPI entered incorrectly
• Incorrect date of service — typo on the DOS
• Eligibility errors — wrong plan billed; correct plan identified

When resubmitting a corrected claim, use the appropriate claim frequency code — typically Frequency Code 7 (replacement) for a corrected claim or Frequency Code 8 (void) when voiding a claim. Payer requirements vary, so verify before resubmitting. Include a cover letter explaining what was corrected.

When to Appeal

Appeal when the denial is not a billing error on your part — when the payer's decision appears to be incorrect, or when you have documentation that supports overturning the denial.

Common situations that call for a formal appeal:

• Timely filing (CO-29) — you have clearinghouse confirmation or electronic proof that the claim was submitted on time
• Medical necessity (CO-50) — clinical documentation supports the service; request peer-to-peer if available and appropriate between the treating provider and the payer's medical director
• Prior authorization denied (CO-15, CO-167) — authorization was obtained but not linked, or was retroactively denied despite meeting criteria
• Duplicate denial (CO-18) — the original claim was never paid and this is not actually a duplicate
• Out-of-network / network gap — the service was referred by an in-network provider, or no in-network provider was available
• Coordination of benefits errors (CO-22) — the COB order was applied incorrectly

Always confirm the appeal deadline before preparing the packet. File early — payers are not required to accept late appeals regardless of the reason.

What Every Appeal Packet Should Include

A complete, well-organized appeal packet gives you the best chance of a favorable outcome. At minimum, every appeal should include:

• Appeal cover letter — clearly stating what is being appealed, why, and what resolution is requested
• Patient name, date of birth, and member ID
• Claim number — the payer's assigned number from the EOB
• Date of service and CPT/HCPCS code(s) being appealed
• Denial code and denial reason — the CARC and RARC from the EOB
• Copy of the original EOB or ERA showing the denial
• Proof of timely filing — clearinghouse confirmation with timestamp (for CO-29 appeals)
• Medical records or clinical documentation — when appealing on medical necessity grounds
• Authorization proof — confirmation number, approval documentation (for auth-related denials)
• Primary EOB — when appealing a secondary payer denial or COB error
• Payer-specific appeal form — if the payer requires their own form in addition to your letter

Keep a copy of everything submitted. Document the submission method (fax, portal, mail), the date submitted, and any confirmation number received.

Track Every Denial

Every denial should go into a tracking system the same day it is found. Not next week. Not when you get to it. The same day — because the appeal deadline is already running.

Your denial tracker should capture at least these fields for every open denial:

Review your denial tracker weekly at minimum. Any denial approaching its deadline without a resolution should be escalated immediately.

Common Denial Workflow Mistakes

These are the mistakes that cost billing offices the most recoverable revenue.

• Waiting too long to review denials. The deadline starts on the denial date. Every day you wait is a day closer to losing the right to appeal.
• Treating all denials the same. A CO-29 needs proof of timely filing. A CO-50 needs clinical records. A CO-18 needs a status check. The action depends on the denial — not just on the fact that the claim wasn't paid.
• Appealing something that should be corrected and resubmitted. If there was a billing error, a formal appeal is not the right path — and it may not be accepted. Correct the error and resubmit.
• Resubmitting something that needed an appeal. Refiling a claim after a medical necessity denial without any supporting documentation will result in the same denial. Some situations require a formal appeal with records.
• Billing the patient for contractual adjustments. A CO-45 reduction is a write-off under your contract. The patient does not owe the contractual adjustment amount. Billing them for it is a contract violation.
• Not billing secondary insurance. When a patient has two plans, the primary EOB is the trigger for secondary billing — not optional additional effort. Missing this step means leaving money on the table and billing the patient for something the secondary may cover.
• Not documenting phone calls. If you call the payer, write down the date, the rep's name, the reference number, and what was said. Verbal commitments from payer reps are not binding unless documented.
• Missing appeal deadlines. This is final. Most payers will not accept a late appeal regardless of the reason. Deadline management is not optional.
• Not attaching proof or documentation. An appeal without supporting documentation is unlikely to succeed. Every appeal should be complete before it is submitted.

Simple Daily Denial Workflow

A consistent daily routine keeps denials from aging into write-offs.

1. Review new EOB and ERA denial lines — check clearinghouse reports and payer portals each morning
2. Add each denial to your tracker — log the denial date, CARC/RARC, amount, and calculate the deadline
3. Sort by deadline and dollar amount — work the most urgent and highest-value denials first
4. Fix quick corrections — demographic errors, missing modifiers, and simple data corrections can often go out the same day
5. Prepare appeal packets — gather records, draft cover letters, and compile documentation for formal appeals
6. Submit appeals and resubmissions — via the payer's required channel; document the submission date and confirmation
7. Set follow-up dates — if no response in 30 days, follow up and document the contact
8. Update final outcomes — when a denial is resolved, close it in the tracker with the final result

A denial that goes unlogged for a week is a denial that may be unrecoverable. The daily habit is what keeps the pipeline clean.

Key Takeaways

• Not all denials are the same. The CARC code tells you the reason — the reason determines the action.
• A rejection and a denial are not the same thing. Rejections are front-end returns without appeal deadlines. Denials appear on EOBs and may have strict deadlines.
• The appeal deadline starts on the denial date — not when you find it. Log every denial the same day it is identified.
• Before acting, answer five questions: what was denied, why, is the denial correct, what is needed, and what is the deadline.
• Correct and resubmit when there was a billing error. Appeal when the denial appears incorrect or when documentation can support reversal.
• Never bill the patient for a CO-45 contractual adjustment. Always bill secondary insurance before billing the patient for a remaining balance, after verifying secondary coverage, payer rules, and practice policy.
• Every appeal packet should be complete before submission — cover letter, EOB copy, claim information, and all relevant supporting documentation.
• Document every payer call: date, rep name, reference number, and what was said.
• Review your denial tracker weekly. Denials approaching their deadline without resolution should be escalated immediately.
• A consistent daily denial workflow — log, sort, fix, appeal, follow up — prevents denials from aging into unrecoverable write-offs.

Related Forms and Templates

Use these free resources from MedicalBillingForms.com to support your denial workflow.

Related Guides

• Reading an EOB: A Practical Guide

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  Before you can work a denial, you need to read the EOB. This guide covers every section of an EOB — header, service lines, CARC/RARC codes, and summary totals — and explains what each column means.

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• Clean Claim Fundamentals

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  The best way to work fewer denials is to submit cleaner claims. This guide covers the elements of a clean claim and the most common errors that cause first-pass rejections and denials.

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• Prior Authorization, Without the Chaos

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  For CO-15 and CO-167 denials involving prior authorization, this guide covers the full PA workflow — from verifying requirements through tracking active authorizations and managing expirations.

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• Coordination of Benefits Explained

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  For CO-22 and COB-related denials, this guide covers how COB order is determined, how to bill primary and secondary correctly, and the most common coordination of benefits errors.

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• Patient Billing & Collections Basics

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  When a denial is pending, patient billing should be on hold. This guide covers when to bill the patient, payment plans, and the balance follow-up sequence.

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Disclaimer

Last reviewed: 2026 · MedicalBillingForms.com · Published by Sunshine Summit Network