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Sample lesson · Bridge to Billing · 22 min

Reading a denial — the top 10 codes.

Welcome to the back of the revenue cycle. The billing team wakes up every morning and looks at a work queue — a list of claims that came back from the insurance company saying "no, not yet, or not for this much." Each claim has a code attached. Learn ten codes and you can read 80% of the denials you'll ever see.

Format · Audio + 5 chapters
Outcome · Identify any of the top 10 denials by code and decide what to do
Difficulty · Intermediate (front office foundation assumed)
Estimated time · 22 minutes
Now playing — Lesson narration 04:12 / 14:30

A denial is not a no. A denial is a question. The insurance company is saying — tell me more, fix this field, prove it. Your job in billing is to translate the question and answer it.

Chapter 3 · Step 3 of 4 Tour · interactive

The work queue you'll inherit on day one.

Every morning, the billing team opens Resolute Professional Billing and pulls up a work queue — a filtered list of claims needing action. Below is what one looks like (a simulated lookalike, not Epic). Hover over the codes; they map to the dictionary in the next step.

WQ-401 · Denial follow-up · 47 claims Simulated
CLM 884213 CO-16 D. Kim · 03/14 office visitMissing/invalid information $185.00 38d
CLM 884225 CO-22 M. Flores · 03/15 annual examCare may be covered by another payer $240.00 37d
CLM 884228 PR-1 P. Romero · 03/15 follow-upPatient deductible $340.00 37d
CLM 884241 CO-50 H. Park · 03/16 MRI lumbarNot deemed medically necessary $1,420.00 36d
CLM 884255 CO-29 L. Ortiz · 12/04 office visitTime limit for filing has expired $185.00 128d
CLM 884262 CO-97 R. Pham · 03/16 procedureBundled payment — already paid $95.00 36d
CLM 884271 PR-3 A. Singh · 03/17 office visitPatient copay $30.00 35d

Notice the pattern: most denials are CO- codes (Contractual Obligation — the payer says "we won't pay this") or PR- codes (Patient Responsibility — the patient owes it). A small number are administrative. The codes tell you what kind of follow-up each claim needs.

The five codes from the queue, decoded.

Each code carries a question. Answer the question, the claim moves.

CO-16

Missing or invalid information

Something on the claim was wrong, missing, or didn't pass a payer edit. Usually: subscriber ID typo, wrong date of service, missing modifier, wrong place of service.

What you do: Open the claim. Compare the demographics on the claim against the chart. Find the bad field, fix it, resubmit. About 60% of CO-16s trace back to a registration error at the front desk.

CO-22

Care may be covered by another payer

The payer thinks somebody else is primary. Common in patients with two insurances (Medicare + supplement, BCBS + spouse's plan). Coordination of Benefits issue.

What you do: Check coverage on file. If there's a primary that wasn't billed, bill primary first, then re-bill secondary with the EOB attached. If the patient hasn't told you about a second plan, call them.

PR-1

Patient deductible

The payer received the claim, processed it, applied it to the patient's deductible. The patient owes this amount. This is not a problem — it's the system working.

What you do: Post the adjustment, send the patient a statement, and if it's a large amount, offer a payment plan. Front office could have flagged this at check-in (HDHP yellow flag).

CO-50

Not deemed medically necessary

The payer decided the service wasn't justified by the diagnosis. Often an MRI or specialty service that needed prior auth and didn't get it, or a diagnosis code that didn't support the procedure.

What you do: Pull the chart. If there's clinical justification, file an appeal with supporting documentation. If prior auth was missed at the front office, this often becomes a write-off.

CO-29

Timely filing limit expired

The claim was submitted too late. Each payer has a window — typically 90 days, sometimes 365. Once it's gone, it's gone. This is the most painful denial because it's almost never recoverable.

What you do: Check the original submission date. If you can prove it was submitted on time and rejected for a reason, file a reconsideration. Otherwise it's a write-off and a process review.

PR-3

Patient copay

The payer applied the contracted copay to the patient's responsibility. The classic "I should have collected this at check-in" denial.

What you do: Post the patient adjustment, bill the patient. Then check why the front office didn't collect — old plan on file? Forgot to ask? This is the feedback loop between billing and front office.

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The connection back to the front desk

Three of the five denials in this work queue trace back to a front office decision: the bad demographics on CO-16, the missed COB on CO-22, and the uncollected copay on PR-3. The front office and the billing department are not separate jobs. They're the same job, eight weeks apart.

Why this lesson exists

Billing is the natural next step from front office.

Every billing team interview asks the same first question: "Tell me about your eligibility experience." Front office MAs are already doing the thinking that billing requires — coverage, payer rules, claim hygiene. They just don't speak the vocabulary yet.

This module gives you the vocabulary. By the time you finish Track 3, you can sit in a billing interview, point to a denial code, and explain what it means and what you'd do about it. That is the bar.

Cheat sheet · the top 10

Print this

CO — payer issues
  CO-16  missing/invalid info
  CO-22  other primary payer
  CO-29  timely filing missed
  CO-50  not med necessary
  CO-97  bundled / inclusive
  CO-167 dx not covered

PR — patient owes
  PR-1   deductible
  PR-2   coinsurance
  PR-3   copay
  PR-204 not covered

Read the code, ask the
question, find the answer
in the chart or the EOB.
Pause & try · cohort exercise

Ask your billing team to show you their work queue.

Most billers will say yes — most have never had a front office MA ask. Spend 15 minutes looking over a shoulder. Count how many of the top 10 codes you see. Post your count and which one came up most.