The Advance Beneficiary Notice (ABN)
The Advance Beneficiary Notice of Noncoverage (ABN) is a standardized written notice that a provider or supplier gives a Medicare beneficiary before furnishing an item or service that Original Medicare is expected to deny, typically because it may not be considered reasonable and necessary. Issued and formatted according to CMS instructions, the notice explains why payment is expected to be denied and lets the beneficiary choose whether to receive the service and accept potential financial responsibility. Because coverage rules, contractor policy, and the notice form itself change over time, providers confirm current requirements with CMS and their Medicare Administrative Contractor (MAC) rather than relying on a fixed rule.
Updated 7 min read
Reviewed by Anwaar Tayyab
Director of Billing Operations ·
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Key takeaways
- An ABN is a CMS-standardized notice used in Original Medicare (fee-for-service Part A and Part B) to inform a beneficiary that a specific item or service is expected to be denied and to transfer potential financial liability.
- It is generally used for services expected to be denied as not reasonable and necessary; it is not used to shift liability for services statutorily excluded from Medicare, though voluntary notices exist.
- A valid ABN is delivered before the service, identifies the specific item, states a reason payment may be denied and an estimated cost, and gives the beneficiary a genuine option.
- When a properly executed ABN is on file, the beneficiary may be billed if Medicare denies the claim; claims often carry a modifier to signal an ABN is on record.
- Specific forms, timing expectations, and applicable services vary by CMS guidance, contractor, service type, and date, so current sources should be verified.
What an ABN is and why it exists
An ABN is a formal, standardized notice used within Original Medicare so a beneficiary can make an informed choice before receiving a service that Medicare is likely to deny. The underlying concept comes from Medicare's limitation-on-liability provisions, which protect beneficiaries from unexpected charges when neither they nor the provider knew a service would be denied. By giving advance written notice, a provider documents that the beneficiary was informed, which is what allows the provider to bill the beneficiary if Medicare later denies the claim.
The notice most commonly applies where a service could be considered not medically necessary under Medicare's coverage rules, such as frequency limits or conditions described in a local coverage determination (LCD). Coverage policy is set through national and local coverage determinations, which change over time, so whether a given service warrants an ABN is a judgment made against current policy.
Scope
When providers issue an ABN
Providers generally consider an ABN when they have a genuine, specific reason to expect Medicare will deny a particular item or service. The notice is not intended to be delivered routinely to every patient or as a blanket disclaimer, and CMS guidance addresses the difference between appropriate case-by-case use and improper routine issuance.
- A service may exceed a coverage frequency limit or fall outside conditions described in an LCD or national policy.
- A service may be considered not reasonable and necessary for the patient's documented condition.
- Certain items or suppliers face mandatory notice expectations under specific Medicare rules that vary by service category.
There is a distinction between services expected to be denied as not reasonable and necessary and services that Medicare never covers because they are statutorily excluded. The mandatory ABN process centers on the former. For excluded services, a provider may still choose to issue a voluntary notice as a courtesy, but the limitation-on-liability protections work differently. Confirming which category applies, and the current instructions for each, is done against CMS guidance rather than a fixed assumption.
Important
What makes a notice valid
For an ABN to support billing the beneficiary after a denial, it generally must be delivered correctly and completed with enough specificity that the beneficiary can make an informed decision. CMS specifies the current form, its fields, and delivery expectations, and these details are periodically revised.
Deliver in advance
The notice is provided before the item or service is furnished, with enough time for the beneficiary to consider options and ask questions.Identify the specific service
It names the particular item or service expected to be denied rather than describing services in vague or blanket terms.State a reason and estimated cost
It gives a plain-language reason payment may be denied and a good-faith cost estimate so the financial stakes are clear.Offer a genuine choice
The beneficiary selects an option indicating whether to receive the service and how they wish the claim to be handled, then signs and dates the notice.
Caution
How the ABN affects claims and liability
When a valid ABN is on file, the provider can submit the claim to Medicare and, depending on the beneficiary's selected option, bill the beneficiary if Medicare denies payment. Medicare claims commonly carry a modifier from the HCPCS code set to signal to the MAC that a notice is on record; other modifiers signal that no notice was obtained. The GA, GX, GY and GZ modifiers are the core set, and which one applies turns on two questions: whether the item is a benefit at all, and whether notice was given. The conventions are defined by CMS and applied according to current instructions.
| Scenario | General effect on beneficiary liability |
|---|---|
| Valid ABN signed; beneficiary elects to receive service and be billed if denied | Provider may bill the beneficiary if Medicare denies the claim |
| No ABN obtained where one was required | Liability generally cannot be shifted; charge may become a write-off |
| Defective or late ABN | May be treated as if no valid notice existed for liability purposes |
| Voluntary notice for a statutorily excluded service | Beneficiary is typically responsible regardless, as the service is never covered |
Effects are general and depend on current CMS rules, the specific service, and how the claim adjudicates.
The outcome ultimately depends on how Medicare adjudicates the claim and on the beneficiary's selected option. Reviewing the remittance advice and the beneficiary's notice together clarifies who bears the balance; see reading the Medicare remittance and MSN for how those documents describe the outcome.
Variation and staying current
Several ABN details are not fixed and should be confirmed against authoritative sources at the time of use. These include the approved form version and its expiration, delivery and retention expectations, which service categories require notice, and modifier conventions.
- Form and instructions
- CMS publishes the standardized notice and its completion instructions, and updates them periodically; providers verify the current version.
- Contractor policy
- MAC-level coverage articles and LCDs shape when a service is likely to be denied, and these differ by jurisdiction and change over time.
- Service-specific rules
- Some categories of items and suppliers have their own notice expectations distinct from the general reasonable-and-necessary use case.
Tip
Frequently asked questions
Is an ABN required for every Medicare patient?
No. The notice is intended for case-by-case use when a provider has a specific, genuine reason to expect Medicare will deny a particular item or service. CMS guidance treats routine, blanket issuance to every patient as improper. Whether a notice is appropriate depends on current coverage policy for the service in question.
Does an ABN guarantee the provider will be paid by the patient?
No. A valid, properly executed ABN generally allows the provider to bill the beneficiary if Medicare denies the claim, but the notice must meet CMS requirements for timing, specificity, reason, cost estimate, and signature. A defective or late notice may fail to shift liability, and the actual outcome depends on how the claim adjudicates.
How does an ABN differ from prior authorization or eligibility verification?
They address different questions. Eligibility verification confirms whether a person has active Medicare coverage, and prior authorization is a pre-service approval process used for certain services. An ABN addresses the expectation that a covered-category service will be denied, usually as not reasonable and necessary, and documents the beneficiary's informed choice to proceed.
Is an ABN used with Medicare Advantage plans?
The ABN is a feature of Original Medicare fee-for-service. Medicare Advantage plans administer coverage under their own rules and use their own beneficiary notices and appeal processes. Providers confirm the specific plan's requirements rather than assuming the Original Medicare process applies.
What happens if the ABN is filled out incorrectly?
A notice that is delivered too late, uses vague or coercive wording, omits the reason or cost estimate, or is unsigned may be considered defective. In that case it generally does not transfer financial responsibility to the beneficiary, and the denied charge may become a provider write-off. Current CMS completion instructions define what makes a notice valid.
Related glossary terms
Terms that appear throughout discussions of the ABN and Original Medicare liability.
Related reading
Continue with closely related topics in the Medicare billing cluster.
National and local coverage determinations
How CMS and contractors define what Medicare considers reasonable and necessary, which drives when an ABN applies.
Common Medicare billing denials
Frequent denial reasons in Original Medicare, including medical-necessity denials tied to notice requirements.
Reading the Medicare remittance and MSN
How remittance advice and the Medicare Summary Notice describe payment outcomes and beneficiary responsibility.
Assignment and participation
How assignment and participation status shape what a provider may bill a Medicare beneficiary.
Chiropractic billing
The specialty where the notice is routine rather than exceptional — once treatment becomes maintenance it stops being covered, and a claim without the AT modifier says so.
ABN issuance checklist
A general, step-oriented checklist for delivering a complete and timely notice.
Authoritative sources
- 42 U.S.C. 1395pp — Social Security Act 1879, limitation on liability where claims are disallowed (opens in a new tab)
United States Code, 2023 Edition (GPO). The statute the ABN exists to satisfy. Subsection (a) provides that where payment may not be made by reason of section 1395y(a)(1) or (9) and both the individual and the provider did not know, and could not reasonably have been expected to know, that payment would not be made, payment shall nonetheless be made. Subsection (c) provides that no payment is made where both the beneficiary and the provider knew, or could reasonably have been expected to know, that payment could not be made — which is why establishing the beneficiary's knowledge in advance is what shifts the charge to the beneficiary.
- eCFR — 42 CFR 411.404, criteria for determining that a beneficiary knew that services were excluded from coverage (opens in a new tab)
The regulation that turns written notice into knowledge. A beneficiary who receives services that are custodial care or that are not reasonable and necessary is considered to have known the services were not covered where written notice was given to the beneficiary, or to someone acting on his or her behalf, that the services were not covered because they did not meet Medicare coverage guidelines — and where that notice came from the QIO, intermediary or carrier, the provider's utilization review body, or the provider, practitioner, or supplier that furnished the service.
- Medicare Claims Processing Manual, Chapter 30 — Financial Liability Protections (opens in a new tab)
Centers for Medicare & Medicaid Services. The operating instructions for the notice. Section 50 identifies the ABN as Form CMS-R-131, issued to Original Medicare fee-for-service beneficiaries and not used for Medicare Advantage or Part D, and lists the statutory denial reasons that make it mandatory. Section 50.2.1 states that ABNs are not required for care that is statutorily excluded but encourages voluntary issuance as a courtesy. Section 40.2.1 requires delivery far enough in advance that the beneficiary can make a rational, informed decision without undue pressure, and notes that last-minute notification can be coercive and a coercive notice is invalid. Section 40's routine notice prohibition rules out generic, blanket, and pre-signed blank notices. Section 50.9 provides that a beneficiary given a properly delivered ABN who agrees to pay may be held liable, and that a beneficiary who does not receive proper notice when required is relieved from liability. Section 30.2.3 records that a provider may signal a valid advance notice on the claim through occurrence code 32 or the applicable HCPCS modifier, and that if the notice is found invalid the contractor overrides the modifier and holds the provider liable.
- ABN form instructions, Form CMS-R-131 (OMB 0938-0566) (opens in a new tab)
Centers for Medicare & Medicaid Services. The completion instructions that define a valid notice field by field. Notifiers must deliver the ABN before providing the items or services, review it with the patient and answer questions before it is signed, allow time to consider the options, and retain a copy. The item column must name the specific items or services; the reason column must explain in plain language why Medicare may not pay, with at least one reason applicable to each item listed; the estimated cost column requires a good-faith effort at a reasonable estimate. The patient or representative must check exactly one of the three options and must sign and date the signature line, which cannot be completed in advance of the rest of the notice; pre-selection of an option by the notifier invalidates the notice. The instructions also note the notice may be used for items Medicare never covers, in which case the patient need not choose an option box or sign.
- Medicare Advance Written Notices of Non-coverage (MLN006266, May 2025) (opens in a new tab)
Centers for Medicare & Medicaid Services, Medicare Learning Network. Its claim reporting modifier table sets out the HCPCS modifiers used to report an advance notice on the claim: GA where a mandatory notice was issued and kept on file, GX where a voluntary notice was issued for care Medicare never covers, GY where the item or service is statutorily excluded or does not meet the definition of a Medicare benefit, and GZ where the provider expects a not-reasonable-and-necessary denial and no notice was issued; two further modifiers cover equipment upgrades. This is the source for the two questions that decide which modifier applies — whether the item is a benefit at all, and whether notice was given.