An Advance Beneficiary Notice of Noncoverage (ABN) is the form a practice gives an Original Medicare patient before a service that Medicare is expected to deny. When the notice is valid, the practice can bill the patient if Medicare does not pay. When it is missing or flawed, the practice usually absorbs the cost. Most ABN problems come from a short list of errors, such as using an outdated form or reporting the wrong modifier.
This post covers when an ABN is needed, how to complete and deliver it, which claim modifiers to use, and what makes a notice invalid.
What Is an ABN?
The ABN, Form CMS-R-131, is a written notice that tells a Medicare fee-for-service patient that Medicare may not pay for a specific item or service, explains why, and gives an estimated cost. The patient then decides whether to receive the service and accept financial responsibility. It applies only to Original Medicare. Medicare Advantage plans do not use the ABN and have their own pre-service determination process.
The form was updated recently. The transition period for the previous version ended May 12, 2026, and for dates of service on or after that date, using an older version invalidates the notice. The current version expires March 31, 2029. Download the current English, Spanish, or large-print version from the CMS ABN page and discard any blank copies of the old one.
When Is an ABN Required?
You need an ABN when you expect Medicare to deny a service that it normally covers because it is not reasonable and necessary for this patient. Common reasons include:
- The diagnosis does not meet the criteria in a local or national coverage determination (LCD or NCD)
- The service exceeds Medicare’s frequency limit
- The documentation suggests Medicare will not consider the service necessary
You do not need one in several situations. Services that Medicare never covers by law, such as routine physicals, most dental care, and cosmetic surgery, do not require an ABN, though you can give a voluntary notice. An ABN also cannot be used in an emergency or when the patient is under duress, and it is not needed for services Medicare is expected to pay.
The notice must be based on a real expectation of denial for that patient and that service. Having every patient sign an ABN before every visit, often called a blanket ABN, is not valid.
What a Valid ABN Contains
The form identifies the notifier and the patient, then names the specific item or service, the reason Medicare may not pay, and an estimated cost. The patient chooses one of three options and signs and dates the form.
- Option 1: The patient receives the service, and Medicare is billed. If Medicare denies it, the patient is responsible and keeps the right to appeal.
- Option 2: The patient receives the service and pays out of pocket. Medicare is not billed, and there is no appeal.
- Option 3: The patient decides not to receive the service and owes nothing.
Staff cannot pick an option for the patient, and the reason has to be specific. “Medicare may not pay” alone is too vague. The cost estimate needs to be a good-faith figure. CMS instructions treat an estimate as reasonable if it falls within the greater of $100 or 25 percent of the actual cost.
How to Deliver the ABN
Give the notice in person when you can, early enough that the patient has time to read it and ask questions before the service. Do not hand it over in an emergency or when the patient is rushed or distressed. If you deliver it by phone, send a copy afterward and document the call. A notice given after the service cannot move liability to the patient for care already provided.
Give the patient a copy and keep the original with the record. CMS instructions call for retaining it for five years, and some states require longer, so check the form instructions and your state rules.
Claim Modifiers for ABN Billing
The notice only protects you if the claim shows what happened. Report the modifier on the line item, which is Item 24D on the CMS-1500 or the equivalent field on the 837P.
| Modifier | Meaning | Who is liable if Medicare denies |
| GA | A required ABN was issued and is on file | The patient |
| GX | A voluntary notice was issued for a service that is statutorily excluded or not a Medicare benefit | The patient |
| GY | The item or service is statutorily excluded or not a Medicare benefit | The patient |
| GZ | Medicare is expected to deny the service as not reasonable and necessary, and no ABN was issued | The provider |
GZ is a self-reported error. It tells Medicare you had no valid notice, and the denial that follows cannot be billed to the patient. Use it only when the ABN was truly missed, and treat each one as a reason to review your front-end process. When Medicare denies a GA claim, you can bill the patient for the denied amount, based on the option the patient chose.
Common ABN Mistakes
The same errors tend to appear in audits and denials:
- Using a previous version of the form for dates of service on or after May 12, 2026
- Leaving the cost estimate blank or the reason too general
- Pre-selecting an option or having staff fill in the patient’s choice
- Missing signature or date
- Issuing blanket ABNs for routine services
- Giving the notice after the service
- Using an ABN for a Medicare Advantage patient
- Billing a service without the GA, GX, GY, or GZ modifier that applies
Several of these can be caught before submission. A claim scrubber with edits for ABN-related modifiers helps, and our post on claim scrubbing techniques explains how to set up useful checks.
When to Get Outside Help
ABN errors usually show up as denials that no one can bill to the patient, which is hard to recover after the fact. Rapid RCM Solutions provides AR and denial management for practices that want help reviewing medical necessity denials, checking modifier use, and tightening the process so fewer of them reach the claim stage.
Conclusion
An ABN protects a practice only when it is the current form, is specific, is delivered before the service, and matches the modifier on the claim. Check that your forms are up to date, train staff to issue notices only when a denial is expected, and review GZ claims for missed notices.
FAQs Medicare ABN Billing Requirements
Do Medicare Advantage patients need an ABN?
No. The ABN is for Original Medicare fee-for-service. Medicare Advantage plans use their own coverage determination process.
Can I bill the patient if I did not give an ABN?
Generally not for a medical necessity denial. If Medicare is expected to deny a service as not reasonable and necessary and no valid ABN was issued, the provider is liable. Report modifier GZ in that case.
What does the GA modifier mean?
GA tells Medicare that a required ABN was issued and is on file. If Medicare denies the service, the patient is responsible for the cost.
Is an ABN needed for services Medicare never covers?
No. Statutorily excluded services do not require one, though you can issue a voluntary notice and report the GX or GY modifier, depending on the situation.
