New Medical Biller
Survival Guide

Medical billing has its own language. Here are the terms you'll hear every single day:

Essential Terms:

• Claim — A formal request to an insurance company for payment for healthcare services rendered. • CMS-1500 — The standard claim form used for professional (non-hospital) billing. • UB-04 (CMS-1450) — The claim form used for facility/hospital billing. • CPT Code — Current Procedural Terminology. A 5-digit code that describes the medical service or procedure performed (e.g., 99213 = office visit, established patient). • ICD-10 Code — International Classification of Diseases, 10th Revision. The diagnosis code that explains why the service was performed (e.g., M54.5 = low back pain). • HCPCS Code — Healthcare Common Procedure Coding System. Similar to CPT but includes supplies, equipment, and services not in CPT (e.g., A0429 = ambulance, BLS). • NPI — National Provider Identifier. A unique 10-digit number for every healthcare provider. • EOB — Explanation of Benefits. A statement from the insurance company explaining what was paid (or denied) on a claim. • ERA — Electronic Remittance Advice. The electronic version of an EOB used for automated payment posting. • CARC — Claim Adjustment Reason Code. The code on an ERA/EOB that explains why a claim was denied or adjusted (e.g., CO-50 = not medically necessary). • RARC — Remittance Advice Remark Code. A secondary code that provides additional detail about the CARC. • Deductible — The amount a patient must pay out-of-pocket before insurance begins to cover services. • Coinsurance — The percentage of the allowed amount the patient pays after the deductible is met (e.g., 20%). • Copay — A fixed amount the patient pays per visit (e.g., $25). • Allowed Amount — The maximum amount the insurance company will pay for a service, per their contract. • Write-off — The difference between the billed charge and the allowed amount. For in-network providers, this is contractual and cannot be billed to the patient. • AR (Accounts Receivable) — Money owed to the practice for services rendered but not yet paid. • Clearinghouse — A third-party service that transmits claims between the provider and the insurance company. • Adjudication — The insurance company's process of reviewing and processing a claim. • Remittance — The payment and accompanying explanation sent by the insurance company.

Payer Types:

• Commercial Payer — Private insurance companies (UHC, Aetna, Cigna, BCBS, Humana). • Medicare — Federal program for people 65+ and certain disabilities. • Medicaid — State/federal program for low-income individuals. • TRICARE — Military health insurance. • Managed Care Plan (MCO) — A health plan that contracts with providers (HMO, PPO, POS).

Understanding the claim lifecycle is the foundation of everything you'll do in billing.

The Claim Lifecycle:

1. Patient Registration — Patient information is collected: name, DOB, insurance card, address, phone. This is where errors start if information is wrong.

2. Eligibility Verification — Before or at the time of service, verify the patient's insurance is active and covers the service being provided.

3. Charge Entry — The provider documents the service performed using CPT codes and the diagnosis using ICD-10 codes. These are entered into the practice management system.

4. Claim Generation — The practice management system generates a CMS-1500 (professional) or UB-04 (facility) claim form with all required fields.

5. Claim Scrubbing — The claim is checked for errors — missing fields, invalid codes, NCCI edits — before submission. This happens in the practice management system or at the clearinghouse.

6. Clearinghouse Submission — The claim is transmitted electronically to a clearinghouse (e.g., Office Ally, Change Healthcare, Avility).

7. Payer Submission — The clearinghouse routes the claim to the correct insurance company using the payer ID.

8. Adjudication — The insurance company reviews the claim, applies their rules, and determines payment. This takes 7-30 days typically.

9. Payment + ERA/EOB — The insurance company sends payment (check or EFT) and an ERA/EOB explaining how the claim was adjudicated.

10. Payment Posting — The payment and adjustments are posted to the patient's account in the practice management system.

11. Denial/Appeal/Resubmission — If the claim was denied, it's investigated, corrected, and resubmitted or appealed.

Key Insight: Most denials are caused by errors in steps 1-4 (front-end). The earlier you catch errors, the cheaper they are to fix. An error caught at registration costs nothing to fix. An error caught after denial costs $25-60 to work.

An ERA (Electronic Remittance Advice) is the electronic version of an EOB. It's the file the insurance company sends to your practice management system that explains how each claim was adjudicated.

What an ERA Contains:

• Payer Information — Which insurance company sent the payment. • Check/EFT Information — The payment amount, check number, and date. • Claim-Level Details — For each claim: patient name, date of service, billed amount, allowed amount, payment amount, adjustment amount, and patient responsibility. • CARC and RARC Codes — If the claim was denied or adjusted, the ERA contains the reason codes explaining why. • Service-Level Details — For each CPT code on the claim: billed amount, allowed amount, payment, and any adjustments.

Why ERAs Matter:

• Automated Posting — ERAs allow your practice management system to automatically post payments and adjustments, saving hours of manual work. • Denial Identification — The CARC/RARC codes on the ERA tell you exactly why a claim was denied, which drives your denial management workflow. • Audit Trail — ERAs provide a complete record of how each claim was adjudicated.

Reading an ERA:

Look for the CARC (Claim Adjustment Reason Code) — this is the primary reason code. Then look for the RARC (Remittance Advice Remark Code) — this provides additional detail. Together, they tell you exactly what happened and what to do next.

Example: CARC CO-50 + RARC N126 means "not medically necessary" + "this service is not covered based on the patient's diagnosis."

Tip: Always match the ERA to the original claim before posting payment. Verify the allowed amount, patient responsibility, and denial codes are correct.

An EOB (Explanation of Benefits) is the statement the insurance company sends to the patient explaining how a claim was processed. It's the patient-facing version of the ERA.

What an EOB Contains:

• Service Details — Date of service, provider name, and type of service. • Billed Amount — What the provider charged. • Allowed Amount — What the insurance company allows (contracted rate). • Deductible/Copay/Coinsurance — What the patient owes. • Insurance Paid — What the insurance company paid. • Patient Responsibility — The total amount the patient owes. • Denial/Adjustment Reason — If the claim was denied, the EOB explains why (in plain language for the patient).

EOB vs. ERA:

• EOB = paper, sent to the patient, plain language. • ERA = electronic, sent to the provider, coded (CARC/RARC).

They contain the same information, just in different formats.

Why EOBs Matter to Billers:

• Patient Calls — When patients call confused about their bill, they're looking at the EOB. You need to understand what they're seeing. • Secondary Billing — When billing a secondary insurance, you often need to attach the primary EOB. • Appeals — The EOB/ERA is your documentation of the denial reason for appeals.

Tip: When a patient calls about a bill, ask them to read the EOB to you. The "patient responsibility" amount on the EOB is what they owe (assuming the claim was processed correctly). If they question a denial, the EOB will state the reason — use that to explain next steps.

A denial means the insurance company received your claim, reviewed it, and decided NOT to pay it. The denial includes a reason code (CARC) explaining why.

Denial vs. Rejection — Know the Difference:

• Denial — The claim was received and adjudicated (processed), but not paid. You can appeal or correct and resubmit. • Rejection — The claim was returned BEFORE adjudication because it had formatting errors. It was never processed. You fix the errors and resubmit as if it's a new claim.

This distinction is critical: denials preserve your timely filing date, rejections do NOT.

Common Denial Reasons (CARC Codes):

• CO-50 — Not medically necessary. The diagnosis doesn't justify the procedure. • CO-197 — Prior authorization absent. You didn't get approval before the service. • CO-29 — Timely filing expired. You submitted the claim too late. • CO-16 — Missing/invalid information. A required field was blank or wrong. • CO-97 — Service bundled. The service is included in another procedure you billed. • CO-4 — Modifier inconsistency. A required modifier was missing or wrong. • CO-27 — Coverage terminated. The patient's insurance wasn't active on the date of service. • CO-11 — Diagnosis inconsistent with procedure. The ICD-10 code doesn't support the CPT code. • CO-22 — Coordination of benefits. Another payer is responsible. • CO-45 — Contractual adjustment. This is NOT a denial — it's the contractual write-off.

What to Do When You Get a Denial:

1. Read the CARC and RARC codes — they tell you exactly why the claim was denied.
2. Investigate the root cause — was it a front-end error (registration, eligibility)? A coding error? A documentation issue?
3. Determine the action — correct and resubmit, or appeal.
4. Document the root cause — so you can prevent it from happening again.

Key Insight: 65-90% of denials are preventable. The most common causes are eligibility errors, prior auth gaps, coding errors, and timely filing lapses — all fixable through process improvement.

A rejection means the claim was returned by the clearinghouse or payer BEFORE it was adjudicated. The claim was never processed — it was bounced back for errors.

Rejection vs. Denial — The Critical Difference:

• Rejection — Claim was never processed. Fix errors and resubmit as a new claim. Does NOT preserve your timely filing date. • Denial — Claim was processed and denied. You can correct and resubmit as a corrected claim (type 7), which preserves your timely filing date.

Common Rejection Reasons:

• Invalid NPI — The provider NPI is wrong, not enrolled, or not in the correct format. • Invalid Member ID — The patient's member ID doesn't match the payer's records. • Missing Required Field — A required CMS-1500 field was left blank (e.g., Box 17 referring NPI). • Invalid CPT/HCPCS Code — The code was deleted or not valid for the date of service. • Invalid Diagnosis Code — The ICD-10 code was deleted or not valid for the date of service. • Payer ID Mismatch — The payer ID on the claim doesn't match the payer routing. • Duplicate Submission — The clearinghouse detected a duplicate transmission.

What to Do When You Get a Rejection:

1. Read the rejection reason — the clearinghouse report will tell you exactly what's wrong.
2. Fix the error — correct the identified field(s) on the claim.
3. Resubmit as a new claim — rejections don't get a corrected claim (type 7). Resubmit as frequency type 1 (original).
4. Monitor for timely filing — since rejections don't preserve the filing date, track the original submission date. If the rejection causes you to miss the filing deadline, you may need a timely filing waiver.

Key Insight: Rejections are your first line of defense. A good claim scrubber will catch most rejections before they reach the payer. Review your clearinghouse rejection reports daily — not weekly — to prevent claims from aging into timely filing risk.

Pro Tip: Keep the clearinghouse 999 acknowledgment and 277CA acceptance reports. These prove the claim was transmitted and accepted by the clearinghouse, which can help with timely filing disputes if the payer later claims they never received it.

An appeal is a formal request to the insurance company to reconsider a denied claim. You appeal when you believe the denial was incorrect — the service was covered, the documentation supports medical necessity, or the denial was based on an error.

When to Appeal vs. Correct and Resubmit:

• Correct and Resubmit — when the claim had an error you can fix (wrong code, missing modifier, wrong patient info). • Appeal — when the claim was correct but the payer denied it in error, or when additional documentation could change the outcome.

The Appeal Process (Typical Levels):

1. First-Level Appeal (Reconsideration) — Submit a written appeal with a cover letter and supporting documentation. Deadline: typically 90-180 days from the denial date. Decision in 30 days.

2. Second-Level Appeal — If the first appeal is denied, you can escalate to a second-level review, often by a different reviewer or an Independent Review Organization (IRO). Deadline: typically 60 days.

3. External Review — If the second appeal is denied, you can request an independent external review by an IRO. Deadline: typically 4 months.

4. State/Federal Escalation — For Medicare, the appeal process goes through 5 levels (Redetermination → Reconsideration → ALJ → Appeals Council → Federal Court). For commercial plans, you can file a complaint with the state Department of Insurance.

How to Write a Successful Appeal:

1. Reference the specific denial — include the claim number, date of service, patient name, and member ID.
2. State the denial reason — cite the CARC code from the ERA/EOB.
3. Explain why the denial is incorrect — be specific and reference the payer's own policy.
4. Attach supporting documentation — clinical notes, medical necessity letter, eligibility verification, clearinghouse reports.
5. Map documentation to criteria — don't just send raw notes; explain how your documentation meets the payer's published criteria.

Appeal Success Rates: • First-level appeals: 30-50% overturn rate • Medical necessity appeals with documentation: 50-70% success • Appeals with a provider letter of medical necessity: significantly higher

Key Insight: Document everything. The strength of your appeal is directly proportional to the quality of your documentation. A peer-to-peer review before filing a formal appeal can often resolve the issue faster.

Prior authorization (prior auth) is the process of getting approval from the insurance company BEFORE providing a service. If a service requires prior auth and you don't get it, the claim will be denied with CO-197 — and the denial is often non-recoverable.

When Prior Auth Is Required:

Each payer has its own auth requirements, but common categories include: • Advanced imaging — MRI, CT, PET, nuclear medicine • Therapy services — PT, OT, SLP (often with visit limits) • Behavioral health at intensive levels — IOP, PHP, RTC • Specialty pharmacy — High-cost medications and infusions • DME — Durable medical equipment and prosthetics • Surgical procedures — Many elective surgeries • Genetic testing — Molecular and genomic testing

The Prior Auth Process:

1. Determine if auth is required — check the payer's auth matrix for the specific CPT code and plan type.
2. Submit the auth request — through the payer portal, by phone, or via fax. Include clinical documentation supporting medical necessity.
3. Wait for the decision — standard auth takes 7-15 days; expedited takes 72 hours.
4. Document the auth number — once approved, enter the auth number in Box 23 of the CMS-1500.
5. Track auth validity — authorizations have start and end dates. Track them so they don't expire before the service.

Common Prior Auth Mistakes:

• Not checking if auth is required — assuming it's not and getting denied later. • Auth for wrong CPT code — the auth covers a different procedure than what was billed. • Auth expired — the auth was valid but expired before the date of service. • Auth for wrong provider/facility — the auth covers a different rendering provider or facility. • Not entering auth number on the claim — auth was obtained but not entered in Box 23.

What to Do if Auth Was Not Obtained:

1. Submit a retro-authorization request — request auth after the service was already provided.
2. Include comprehensive clinical documentation — prove medical necessity at the time of service.
3. Retro-auth success varies — commercial payers ~30-40%, Medicaid ~60%, Medicare rarely grants retro-auth.
4. If retro-auth is denied — file a formal appeal with clinical documentation.
5. If appeal is denied — you may need to write off the loss. Use this as a learning opportunity to prevent recurrence.

Key Insight: CO-197 (prior auth absent) is one of the most expensive preventable denials because it often involves high-cost services. The fix is always prevention — maintain a payer-specific auth matrix and verify requirements before scheduling every service.

Eligibility verification is the process of confirming that a patient's insurance is active and covers the services you're going to provide. It's the single most impactful denial prevention step you can take.

Why Eligibility Verification Matters:

Up to 50% of denials are caused by front-end eligibility issues: • Coverage was terminated (CO-27) • Patient not identified as a member (CO-31) • Wrong payer billed (CO-109) • Coordination of benefits issues (CO-22) • Services not covered (CO-96)

All of these are preventable with proper eligibility verification.

What to Verify:

1. Active coverage — Is the insurance active on the date of service? Check effective and termination dates.
2. Correct member ID — Does the member ID match the insurance card exactly?
3. Plan type — Is it PPO, HMO, EPO, or POS? This affects referrals and auth requirements.
4. In-network status — Is your practice in-network for this plan?
5. Benefits for the specific service — What are the benefits for the specific CPT code you're billing?
6. Deductible status — How much of the deductible has been met year-to-date?
7. Coinsurance/copay — What will the patient owe?
8. Prior auth requirements — Does this service require authorization?
9. COB — Does the patient have other insurance? If so, which is primary?
10. Timely filing limit — What's the payer's filing deadline?

How to Verify Eligibility:

• Payer Portal — Most payers offer real-time eligibility through their provider portal (270/271 transactions). • Phone — Call the payer's provider line. Always ask for a call reference number. • Clearinghouse — Many clearinghouses offer batch eligibility checks. • Practice Management System — Many systems have integrated eligibility verification.

Best Practices:

• Verify for every patient, every visit — eligibility can change. Don't assume coverage from last visit still applies. • Verify before the service — not after. Catching eligibility issues at registration saves denials. • Document everything — record the date, time, representative name, and call reference number. • Re-verify for high-risk patients — patients with recent job changes, Medicaid patients, or those near coverage transitions.

Key Insight: If you only do one thing to reduce denials, make it eligibility verification. It prevents the largest category of denials and is the cheapest to fix — catching an eligibility issue at registration costs nothing; catching it after a denial costs $25-60 per claim to work.

Every medical biller starts somewhere. Here are the most common mistakes new billers make — and how to avoid them.

1. Not Verifying Eligibility This is the #1 mistake. New billers often assume the insurance information from last visit is still valid, or they skip verification when they're busy. Always verify eligibility for every patient, every visit.

2. Confusing Rejections with Denials New billers often treat rejections and denials the same way. They're different: rejections are returned before processing (resubmit as new), denials are processed and denied (resubmit as corrected, type 7). Know the difference — it affects your timely filing.

3. Resubmitting Denials as New Claims When correcting a denied claim, resubmit as a corrected claim (claim frequency type 7), not as a new original claim (type 1). Resubmitting as a new claim creates a duplicate (CO-18) and doesn't preserve your timely filing date.

4. Not Reading the RARC Code When you get a CO-16 (missing information), the RARC code tells you exactly which field is missing. New billers often ignore the RARC and try to guess. Always read both the CARC and RARC.

5. Not Keeping Clearinghouse Reports If a payer claims they never received your claim, the clearinghouse 999 acknowledgment and 277CA acceptance reports are your proof of timely submission. New billers often don't save these — and can't appeal timely filing denials without them.

6. Not Knowing Each Payer's Timely Filing Limit Timely filing limits vary by payer — Medicare is 365 days, UHC is 90 days, some BCBS plans are 180 days. New billers assume all payers have the same limit. Always verify the specific payer's deadline.

7. Not Documenting Payer Calls Every time you call a payer, document: date, time, representative name, ID number, call reference number, and a summary of the conversation. New billers often skip this — then can't prove what was said during appeals.

8. Billing the Patient for Contractual Write-offs CO-45 is a contractual adjustment — the difference between your billed charge and the allowed amount. You CANNOT bill the patient for this. New billers sometimes try to bill patients for contractual write-offs, which violates provider agreements.

9. Not Checking NCCI Edits NCCI (National Correct Coding Initiative) edits flag code combinations that can't be billed together. New billers often submit multiple procedures without checking NCCI, resulting in CO-97 (bundling) denials. Always check NCCI before submitting multi-procedure claims.

10. Not Understanding Modifiers Modifiers change the meaning of a CPT code. Common ones: 25 (significant, separately identifiable E/M), 59 (distinct procedural service), 50 (bilateral), 51 (multiple procedures), 26 (professional component), TC (technical component). New billers often append wrong modifiers or miss required ones.

11. Not Requesting Peer-to-Peer Reviews Most payers offer peer-to-peer reviews before a formal appeal. These are faster and more effective than formal appeals. New billers skip this step and go straight to formal appeals.

12. Not Tracking Denial Trends New billers work denials one at a time without looking for patterns. If you're getting the same denial code repeatedly, there's a systemic issue. Track denial trends by code, payer, and provider to identify root causes.

Key Insight: The best billers are not the ones who work denials fastest — they're the ones who prevent denials from happening in the first place. Focus on the front end (eligibility, auth, coding) and the back end (denials) will shrink dramatically.