Glossary · Billing
Advance Beneficiary Notice (ABN)
An Advance Beneficiary Notice of Noncoverage (ABN) is a written notice providers and suppliers must deliver to Original Medicare (Part B) beneficiaries before furnishing an item or service that Medicare is expected to deny, transferring potential financial liability to the patient when properly executed.
Verified May 8, 2026 · 6 sources ↓
Definition
Source · Editorial summary grounded in 6 cited references ↓
The ABN (form CMS-R-131) is CMS's mechanism for shifting payment responsibility from the provider to the Medicare beneficiary in situations where a claim is anticipated to be denied—most commonly for lack of medical necessity, unmet supplier-number requirements, a denied prior authorization, or prohibited solicitation contacts. The provider must complete the form in full, review it with the patient before the service is rendered, and allow the patient enough time to make an informed choice among the three option boxes: accept the service and financial responsibility (Option 1), accept the service and financial responsibility but decline a Medicare claim submission (Option 2), or decline the service entirely (Option 3). The form is never valid in emergency situations, and providers who skip the ABN when one is required cannot bill the patient if Medicare denies the claim.
The current OMB-approved version of the ABN carries control number 0938-0566 and an expiration date of March 31, 2029. CMS approved this version on March 13, 2026; providers were permitted to use the prior version through May 12, 2026, but must use the current form for all dates of service after that transition deadline. The ABN must be reproduced on a single letter- or legal-size page, and the provider must retain a signed copy on file.
The ABN applies exclusively to Original Medicare fee-for-service (Part B and, in specific contexts, Part A for home health, hospice, and SNF Part B services). It does not apply to Medicare Advantage (Part C) or Part D plans, which operate under separate notice requirements. Statutorily excluded services—items Medicare never covers under any circumstance—do not require an ABN, though providers may issue a voluntary ABN as a courtesy to inform patients of their out-of-pocket exposure.
Why it matters
Skipping a required ABN is not a paperwork technicality—it is a direct financial liability event. When a provider fails to issue an ABN before performing a service that Medicare subsequently denies for lack of medical necessity, Medicare assigns liability to the provider, not the patient, and the provider must write off the charge entirely. Conversely, a properly executed ABN with the GA modifier appended to the claim triggers an automatic Medicare denial that the patient can appeal and that secondary insurers often require before processing their own payment. In orthopedic practice, high-scrutiny services such as non-covered DME, certain imaging ordered outside local coverage determination (LCD) indications, and investigational procedures are ABN flashpoints; a single missed ABN on a high-cost item can exceed thousands of dollars in unrecoverable revenue per occurrence, and a pattern of omissions can attract post-payment audit activity.
Common mistakes
Where people most often go wrong with this concept.
Source · Editorial brief grounded in cited references ↓
- Issuing the ABN at the time of service or after the patient is already in the procedure room—the form must be delivered far enough in advance for the patient to genuinely consider their options and, if they choose, seek the service elsewhere.
- Using an expired version of form CMS-R-131 after the mandatory transition deadline; an ABN executed on a superseded form version is not considered valid by Medicare.
- Issuing an ABN for Medicare Advantage (Part C) patients—the CMS-R-131 form is restricted to Original Medicare, and using it for MA enrollees does not transfer liability.
- Failing to append modifier GA to a claim when a required ABN is on file; without GA, Medicare's system will not register the waiver of liability, and the denial may incorrectly assign financial responsibility to the provider.
- Appending modifier GZ (service expected to be denied, ABN not issued) when an ABN was actually obtained—GZ signals no ABN exists and bars patient billing, the opposite of the intended outcome.
- Leaving the estimated cost field blank or writing a vague range so wide it provides no real notice; CMS requires a specific estimated dollar amount or a good-faith estimate narrow enough to be meaningful.
- Assuming a blanket or standing ABN issued at the start of a care episode covers all future services—ABNs must be service-specific and renewed whenever circumstances change or a new denial risk arises.
- Issuing an ABN for statutorily excluded services (e.g., routine foot care in non-qualifying patients) as if it were mandatory, which it is not, without understanding that a voluntary ABN for excluded services does not require option-box selection or a signature.
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 6 cited references ↓
01Does an ABN apply to Medicare Advantage plans?
02When is an ABN not required even for Original Medicare patients?
03What happens if I perform a service without a required ABN and Medicare denies the claim?
04Can one ABN cover multiple future visits or a course of treatment?
05Which modifier do I use when a required ABN is on file?
06Is the most recent ABN form really mandatory, or can I keep using an older version?
07What must the ABN's estimated cost field contain?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01cms.govhttps://www.cms.gov/medicare/forms-notices/beneficiary-notices-initiative/ffs-abn
- 02cms.govhttps://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNProducts/ABN-Tutorial/formCMSR131tutorial111915f.html
- 03cms.govhttps://www.cms.gov/medicare/medicare-general-information/bni/downloads/abn-form-instructions.pdf
- 04cgsmedicare.comhttps://www.cgsmedicare.com/jc/claims/sub/abns.html
- 05aapc.comhttps://www.aapc.com/blog/29854-modifiers-tell-the-full-story-of-an-advanced-beneficiary-notice/
- 06CMS Internet-Only Manual, Pub. 100-04, Chapter 30 — https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/Downloads/clm104c30.pdf
Mira AI Scribe
When Mira detects a procedure or DME item flagged under an applicable LCD or NCD as potentially not meeting medical necessity criteria—or when a prior authorization has been denied—the scribe layer should surface an ABN prompt before the encounter is finalized. Specifically: (1) Flag the relevant CPT or HCPCS code against active LCD indications for the patient's diagnosis codes; if the documented diagnosis does not appear in the covered indications, annotate the charge line for ABN review. (2) If the ordering provider confirms the service will proceed, recommend appending modifier GA to the claim line and confirm that a signed CMS-R-131 (current OMB-approved version, expiration 03/31/2029) is on file before submission. (3) If no ABN was obtained, flag the line for modifier GZ and alert the billing team that the patient cannot be billed if the claim is denied. (4) Do not generate an ABN prompt for Medicare Advantage plans, Part D items, emergency services, or services that are statutorily excluded from Medicare coverage (use modifier GY for excluded services instead). (5) For Option 1 selections where the patient wants a formal Medicare denial for secondary insurance purposes, confirm the claim will be submitted to Medicare regardless of expected outcome. Document the ABN issuance date and the patient's selected option in the encounter note for audit trail purposes.
See Mira's approachRelated terms
A Local Coverage Determination (LCD) is a regional Medicare policy issued by a Medicare Administrative Contractor (MAC) that defines when a specific service, procedure, or supply is considered reasonable and medically necessary within that contractor's jurisdiction.
A National Coverage Determination (NCD) is a formal, evidence-based ruling issued by CMS that establishes whether Medicare will cover a specific item or service across all Medicare contractors nationwide. NCDs are binding on every Medicare Administrative Contractor and supersede any conflicting local policy.
Medical necessity is the standard requiring that a service or item be reasonable and appropriate for diagnosing or treating a patient's condition according to accepted clinical practice. Payers—including Medicare—use this standard to determine whether a claim will be covered and paid.
Prior authorization (PA) is a payer requirement that a provider obtain approval before delivering a specific service, procedure, or item—otherwise the claim will be denied regardless of medical necessity. Approval is granted when submitted clinical documentation meets the payer's coverage criteria.