Advance Beneficiary Notice (ABN): The Complete Guide
Medicare's Advance Beneficiary Notice of Noncoverage (CMS-R-131) protects both providers and patients when a covered service may be denied. Get the form wrong, and your practice absorbs the cost. This guide covers when an ABN is required, how to complete every field, the three patient options, modifier rules, and the most common mistakes that lead to denied claims.
CMS-R-131
Official ABN form number required by Medicare
100%
Patient liability shifts to you without a valid ABN
Before
ABN must be issued before services are provided
When Is an ABN Required?
An ABN is required whenever you, as a provider or supplier, believe Medicare may deny payment for a service that Medicare would typically cover. The key word is “may” — if you have reason to believe the claim will be denied, you must notify the patient in advance. This is governed by Medicare Claims Processing Manual, Ch. 30, §50.
ABN Required
- A specific service or item you believe Medicare may not cover as medically necessary
- A service that exceeds Medicare frequency limitations (e.g., more than one wellness visit per year)
- Items or services that do not meet Medicare's coverage criteria for the patient's diagnosis
- Lab tests ordered without a diagnosis that supports medical necessity
- Durable medical equipment (DME) that Medicare may consider not reasonable and necessary
- Home health services that may not meet homebound or skilled-care requirements
ABN Not Required
- Services Medicare never covers (use the GY modifier instead — e.g., cosmetic surgery, routine dental)
- Emergency or urgently needed services
- Services provided to patients enrolled in Medicare Advantage (Part C) plans
- Services for patients who are not Medicare beneficiaries
- Screening services with statutory coverage (like annual wellness visits within frequency limits)
Critical Timing Rule
The ABN must be delivered before the service is provided. An ABN presented after the fact is invalid, and the provider absorbs the cost. The only exception is for ongoing or recurring services where a blanket ABN covers a defined period. See our common compliance violations guide for more examples of timing mistakes.
The Three Patient Options on an ABN
Every ABN form presents the beneficiary with exactly three choices. Understanding each option is essential for front-desk staff, billing teams, and compliance officers. The patient's selection directly determines your billing workflow and modifier usage.
Option 1
“I want the items/services. I may be billed.”
What it means
The patient wants to receive the service and agrees to pay out of pocket if Medicare denies the claim.
Billing action
Submit the claim to Medicare with the GA modifier. If denied, bill the patient.
When patients typically choose this
The patient values the service and is willing to accept financial responsibility.
Option 2
“I want the items/services. Don't bill Medicare.”
What it means
The patient wants the service but does not want the claim submitted to Medicare at all.
Billing action
Do not submit a claim to Medicare. Bill the patient directly. No modifier needed.
When patients typically choose this
The patient prefers to pay privately and avoid a denial on their Medicare record.
Option 3
“I don't want the items/services.”
What it means
The patient declines the service entirely after being informed of the potential cost.
Billing action
No claim is submitted. No charge to the patient. Document the refusal in the patient's chart.
When patients typically choose this
The patient decides the service isn't worth the potential out-of-pocket cost.
What If the Patient Doesn't Choose?
If a patient refuses to select an option or sign the ABN, note “Patient refused to sign” on the form, date it, and have a witness sign. The ABN is still considered delivered. However, without Option 1 selected, you cannot hold the patient financially liable for denied services.
How to Fill Out the ABN Form (CMS-R-131)
The CMS-R-131 form has specific fields that must be completed correctly for the ABN to be valid. An incomplete or improperly filled form gives patients grounds to dispute liability. Walk through each field carefully using our guide below, and review your compliance checklist to verify your ABN process is documented.
Header (A)
Notifier Information
- Enter the provider, supplier, or facility name as it appears on your Medicare enrollment
- Include full address and phone number
- Use your NPI-linked business name, not a DBA or marketing name
Common mistake: Using an abbreviated name that doesn't match your Medicare enrollment can invalidate the ABN.
Header (B)
Patient Information
- Enter the patient's full legal name (matching their Medicare card)
- Include their Medicare Beneficiary Identifier (MBI)
- Double-check the MBI against the card — transposed digits are a common error
Common mistake: Pre-printing patient names with just 'First Last' without verifying the legal spelling.
Section (D)
Items or Services
- List each specific item or service that may not be covered
- Use plain language the patient can understand, not CPT codes alone
- Be specific: 'Vitamin D blood test (CPT 82306)' not just 'lab work'
- For multiple services, list each on a separate line
Common mistake: Vague descriptions like 'services rendered' or 'tests' make the ABN invalid.
Section (E)
Reason Medicare May Not Pay
- Explain in plain language why you expect denial
- Check the appropriate box: 'not medically necessary' or 'not covered'
- If frequency is the issue, state the limit: 'Medicare covers 1 per year; this is your 2nd'
- Avoid medical jargon — the patient must genuinely understand
Common mistake: Leaving this blank or writing 'Medicare guidelines' without specifics.
Section (F)
Estimated Cost
- Provide a good-faith dollar estimate of what the patient may owe
- Use a range if the exact cost is uncertain (e.g., '$150-$250')
- This estimate is required — you cannot leave it blank
- Base the estimate on your standard fee schedule
Common mistake: Leaving the cost blank. CMS considers an ABN without cost estimates to be defective.
Section (G-H)
Patient Signature & Date
- Patient selects one of the three options (1, 2, or 3)
- Patient signs and dates the form
- Give the patient a copy of the signed ABN immediately
- Retain the original in the patient's medical record
Common mistake: Having patients sign before filling in sections D, E, and F (blank ABN signing).
ABN Modifiers: GA, GX, GZ & GY
Modifiers tell Medicare what happened with the ABN process. Using the wrong modifier can result in write-offs, audit flags, or improper patient billing. Your clinical documentation should clearly support the modifier you select on each claim.
| Modifier | ABN Status | Patient Liability | Provider Liability |
|---|---|---|---|
| GA | Valid ABN on file | Yes — patient pays | No |
| GX | Voluntary ABN on file | N/A (excluded service) | No |
| GZ | No valid ABN | No | Yes — provider absorbs cost |
| GY | Not needed (excluded) | Yes — patient pays | No |
Mandatory ABN on File
When to use: You issued a valid ABN before providing the service and the patient selected Option 1 (wants the service, may be billed).
Effect on claim: If Medicare denies the claim, liability automatically transfers to the patient. Medicare processes the claim and sends the denial to both you and the patient.
Example
A physician orders a Vitamin D test for a patient. The diagnosis doesn't meet medical necessity criteria. The office issues an ABN, the patient selects Option 1, and the claim is submitted with modifier GA.
Voluntary ABN on File
When to use: You issued an ABN for a service that is statutorily excluded from Medicare coverage (Medicare never covers it), and the patient acknowledges the exclusion.
Effect on claim: Medicare will deny the claim automatically. The voluntary ABN documents that the patient was notified in advance. Liability cannot be assigned since the item was never covered.
Example
A dermatology office provides a cosmetic mole removal. They issue a voluntary ABN to document the patient understands Medicare doesn't cover cosmetic procedures, then bill with GX.
No Valid ABN on File
When to use: An ABN should have been issued but was not, or the ABN on file is invalid (missing fields, delivered after the service, etc.).
Effect on claim: Medicare processes and denies the claim. The provider cannot bill the patient — the provider absorbs the full cost. Using GZ is essentially an admission that you failed to follow ABN procedures.
Example
A physical therapy office realizes after the visit that the patient's 12th session exceeds the therapy cap. No ABN was given. They must submit with GZ and write off the denied amount.
Statutory Exclusion (No ABN Needed)
When to use: The service is statutorily excluded — Medicare never covers it under any circumstances. No ABN is required.
Effect on claim: Medicare auto-denies the claim. The provider can bill the patient directly because the service was never a covered benefit.
Example
A practice bills for hearing aids (excluded from Medicare Part B). No ABN is needed — submit with GY to generate a denial the patient can use for secondary insurance.
7 Common ABN Mistakes That Lead to Denied Claims
Even practices with good intentions make ABN errors that cost thousands in write-offs each year. These mistakes frequently surface during compliance audits and can escalate to fraud allegations in severe cases.
1. Delivering the ABN After the Service
The mistake: Handing the ABN to the patient during checkout or after the procedure has already been performed.
Consequence: The ABN is invalid. You cannot transfer liability to the patient, and the provider absorbs the denied amount.
Fix: Build ABN delivery into the check-in process. Flag appointments that may need an ABN during scheduling.
2. Using Blank or Pre-Signed Forms
The mistake: Having patients sign blank ABN forms during intake 'just in case,' then filling in the details later.
Consequence: CMS considers blank ABNs invalid. If audited, all claims billed under these ABNs could be reversed.
Fix: Complete sections D, E, and F before presenting the form to the patient. Never pre-sign.
3. Vague Service Descriptions
The mistake: Writing generic entries like "lab work," "office visit," or "services" instead of specific items.
Consequence: The ABN fails the 'plain language' requirement. Patients can argue they didn't understand what they were agreeing to.
Fix: Be specific: "Complete blood count (CBC)" not "blood test." Include CPT codes alongside plain descriptions.
4. Missing Cost Estimates
The mistake: Leaving section F (estimated cost) blank or writing 'unknown.'
Consequence: An ABN without a cost estimate is defective per CMS guidelines. The patient can challenge liability.
Fix: Provide a good-faith estimate based on your fee schedule. A range (e.g., '$120-$180') is acceptable.
5. Issuing ABNs for Every Service as a Blanket Policy
The mistake: Requiring all patients to sign ABNs for every visit as a "just in case" practice.
Consequence: CMS considers routine ABN issuance to be an abuse of the process. It can trigger audits and penalties.
Fix: Only issue ABNs when you have a specific, articulable reason to believe Medicare may deny the claim.
6. Not Giving the Patient a Copy
The mistake: Collecting the signed ABN but failing to provide the patient with their copy.
Consequence: Violates CMS requirements. If challenged, lack of patient copy weakens your position.
Fix: Make it a standard workflow step: sign, copy, give copy, file original. Use carbon forms or scan immediately.
7. Using the Wrong Modifier on the Claim
The mistake: Submitting with GA when no ABN was obtained, or using GZ when a valid ABN exists.
Consequence: GA without an ABN on file is fraud. GZ with a valid ABN means unnecessary revenue loss.
Fix: Create a modifier reference card for billing staff. Audit modifier usage monthly.
ABN Decision Flowchart
Use this flowchart to determine whether an ABN is needed and which modifier to apply. Print it and post it in your billing area.
Blanket ABNs for Recurring Services
For patients receiving ongoing services that may not meet Medicare coverage criteria, CMS allows a single “blanket” ABN to cover a defined period rather than issuing a new form at every visit. This reduces administrative burden while maintaining compliance. Keep your compliance work plan updated with blanket ABN expiration dates so nothing slips through the cracks.
When You Can Use a Blanket ABN
- Recurring services provided on a predictable schedule (e.g., weekly physical therapy, monthly lab draws)
- The same service or same category of services each time
- You have an ongoing, reasonable expectation that Medicare may deny
Time Limits and Renewal
- A blanket ABN is valid for up to one year from the date of signature
- Must be renewed annually — set calendar reminders 30 days before expiration
- If the service changes or a new service is added, a new ABN is required
- If the reason for expected denial changes, issue a new ABN
Required Documentation
- List all recurring services covered by the blanket ABN individually
- Include estimated cost for each service (not just a total)
- Note the effective date range on the form
- Keep the blanket ABN in the patient's chart with a clear expiration flag
“A blanket ABN saves time, but only if your tracking system is airtight. One expired blanket ABN can mean months of unrecoverable write-offs.”
Quick Reference: ABN Cheat Sheet
Form required
CMS-R-131 (Advance Beneficiary Notice of Noncoverage). Must be the current approved version — check CMS.gov for updates.
When to issue
Before any Medicare-covered service you expect will be denied. Not for statutory exclusions (use GY instead).
Valid ABN requirements
Specific service description, plain-language denial reason, cost estimate, patient option selected, patient signature, and copy provided to patient.
Modifier Quick Reference
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