Last week a practice manager showed us a stack of Advance Beneficiary Notices her front desk had collected in February. Every Medicare patient who had a vitamin D test had signed one, because "Medicare sometimes denies vitamin D." The forms had no estimated cost filled in, the reason line read "may not be covered," and half were signed after the blood had been drawn. Not one of them would have held up if a patient had disputed a bill. The desk was doing the work, in good faith, and producing paper that protected nobody.
The timing of that conversation was useful, because the form itself has just changed. On March 13, 2026, the Office of Management and Budget approved a revised Form CMS-R-131, the Advance Beneficiary Notice of Noncoverage. The new version carries an expiration date of March 31, 2029. CMS is allowing the prior version, which had been due to expire on January 31, 2026, to remain in use through May 12, 2026; from May 13 the new form is mandatory. The changes are to readability and layout rather than to the rules, and English and Spanish versions are both available on the CMS forms page.
So this is a good month to replace the form and to fix the workflow around it. This article covers when to issue an ABN, when you must not, how to complete it so it is valid, and the GA, GX, GY and GZ modifiers that tell the Medicare claims system who is liable when the service denies.
Key takeaways
- The revised ABN, Form CMS-R-131, is approved from March 13, 2026 and must be in use by May 12, 2026; the rules for using it did not change.
- An ABN is required only for traditional Medicare Part B patients, before a service Medicare usually covers but may deny in this case; it is never used for Medicare Advantage members.
- Blanket or routine ABNs are prohibited; the form must name the specific service, a specific reason and an estimated cost.
- Modifier GA on the claim tells Medicare a valid ABN is on file, so a denial comes back as patient responsibility; GZ tells Medicare there is none, and you eat the denial.
- GY and GX handle statutorily excluded services, where the ABN is voluntary and Medicare will not pay regardless.
What an ABN is and who it is for
The Advance Beneficiary Notice of Noncoverage is the written notice a provider gives a traditional Medicare beneficiary before furnishing an item or service that Medicare would normally cover but is expected to deny in this particular case. Its purpose is to shift financial liability: under the limitation on liability rules, a provider who did not know and could not reasonably have known that Medicare would deny a service cannot bill the patient. The ABN is how you prove the patient was told in advance and chose to receive the service anyway.
It applies to Medicare Part B fee-for-service, including services by physicians, labs, therapists, suppliers and hospital outpatient departments. It does not apply to Medicare Advantage. Plans have their own pre-service process, the organization determination, and a Medicare Advantage member who signs an ABN has signed a form that has no legal effect; you cannot bill them on the strength of it. Check the plan type before the form comes out of the drawer.
A glossary line for physicians: "not reasonable and necessary" is the Medicare standard under Section 1862(a)(1)(A) of the Social Security Act for denying a covered service in a specific case. Frequency limits in a Local Coverage Determination, a diagnosis that does not support the test, an experimental use, and custodial care are the everyday examples. That is the territory the ABN covers.
When to issue an ABN: required, optional and prohibited
Required: when you expect Medicare to deny a normally covered service as not reasonable and necessary for this patient, for example a screening test more often than the coverage rule allows, a lab test ordered with a diagnosis the LCD does not list, or a therapy visit past the point where documentation supports it. Issue the notice before the service, far enough in advance that the patient can consider it and ask questions, and in person where possible.
Optional: for services that are statutorily excluded from Medicare, such as routine physicals, most dental care, hearing aids, cosmetic procedures and items Medicare never covers. Medicare will deny these regardless of notice, and the patient is liable regardless. Practices issue a "voluntary" ABN here as a courtesy so the patient understands the bill; the form allows it, and the claim carries different modifiers, covered below.
Prohibited: routine or blanket ABNs given to every patient "just in case," ABNs with no specific service or reason, ABNs issued in an emergency or under duress, and ABNs for services you have no genuine reason to expect Medicare to deny. CMS is explicit that a generic ABN is invalid, and a pattern of them is a compliance problem. The vitamin D stack in the opening paragraph fails on this point alone.
Completing the form so it holds up
The revised form keeps the same structure. The notifier section identifies the practice. The patient identification section takes the name and an identification number (not the Medicare number). The table lists the specific item or service, the reason Medicare may not pay, in language the patient can understand, and the estimated cost. CMS expects the estimate to be within $100 or 25 percent of the actual charge, whichever is greater; an estimate that is wildly off can invalidate the notice. Then the patient chooses one of three options and signs and dates.
Option 1 means the patient wants the service, wants you to bill Medicare, agrees to pay if Medicare denies, and keeps appeal rights. This is the option that lets you bill the patient after a denial. Option 2 means the patient wants the service and does not want Medicare billed; you may collect at the time of service and there is no Medicare appeal. Option 3 means the patient declines the service. The patient picks; staff may not pre-check a box. Give the patient a copy and keep the original with the record.
| Situation | Is an ABN required? | Claim modifier | What the remit will show | Who pays |
|---|---|---|---|---|
| Covered service, expected denial as not reasonable and necessary, valid ABN signed (Option 1) | Yes | GA | Denial as PR (patient responsibility), commonly PR-50 with the policy remark | Patient, at your charge or as the ABN estimated |
| Covered service, expected denial, no ABN or invalid ABN | Yes, but not obtained | GZ | Automatic denial as CO; no appeal on liability | Practice writes it off; patient cannot be billed |
| Statutorily excluded service (never covered), no ABN | No | GY | Denial as PR, non-covered | Patient |
| Statutorily excluded service, voluntary ABN signed | No (voluntary) | GX with GY | Denial as PR, non-covered | Patient, with a signed acknowledgment on file |
| Medicare Advantage member | Never; ABN has no effect | None; use the plan's organization determination process | Per plan | Per plan rules |
A worked example
A 71-year-old traditional Medicare patient asks for a vitamin D level (CPT 82306). She had one four months ago that was normal, and your Medicare contractor's coverage article limits testing to specific diagnoses and intervals. You expect a denial. Before the draw, the medical assistant completes the ABN: item "Vitamin D blood test (82306)"; reason "Medicare covers this test only for certain conditions and only at certain intervals, and your last test was four months ago with a normal result"; estimated cost $48. The patient chooses Option 1, signs and dates, and receives a copy.
The claim goes out with 82306-GA. Medicare denies the line as PR-50 with a remark pointing to the coverage article. Because the group code is PR, your system moves $48 to the patient balance and the statement goes out. Had the ABN been signed after the draw, or had the reason line said "may not be covered," the correct modifier would have been GZ, the denial would have arrived as CO, and the practice would have absorbed it.
One more layer: if the patient is a Qualified Medicare Beneficiary (a dual-eligible category shown on the Medicare eligibility response), federal law prohibits billing her for Medicare cost sharing, and an ABN does not change that for covered services. Check the eligibility response for QMB status before you rely on any ABN.
Questions we hear
Can the lab issue the ABN instead of us?
The entity that bills Medicare is responsible for the notice, but a lab may not be able to see the patient before the draw, so the ordering practice commonly issues the ABN on the lab's behalf and sends it with the requisition. Agree the process with your reference lab in writing so both sides know who issues, who keeps the original and who bills the patient.
How long do we keep signed ABNs?
Keep them with the medical record for as long as you keep the record, and at least five years from the date of service, which is the retention period CMS expects for ABNs. Scan them into the chart under a document type you can search, because the day a patient disputes a bill is the day you need to find it.
Does the new form change what we type into the EHR?
No. The fields are the same; the layout and wording were simplified. Replace the PDF or template in your EHR and on your intake tablets with the version dated for the March 2026 approval, confirm the Spanish version is loaded too, and retire the old one no later than May 12, 2026. Test the print output; some EHR templates are hard-coded to the old page layout.
What to do this week
- Download the revised Form CMS-R-131 in English and Spanish from the CMS forms page and load it into your EHR and intake tablets; set the old version to retire by May 12, 2026.
- Audit the ABNs signed in January and February for a specific service, a specific reason, an estimated cost, a patient-selected option, and a signature date before the service.
- Write a one-page list of the services in your practice that regularly need an ABN, with the coverage rule and a plain-language reason for each.
- Check that your billing system applies GA, GZ, GY and GX correctly and that PR denials with GA route to the patient statement rather than the denial worklist.
- Add a QMB and plan-type check to the ABN step so Medicare Advantage members and QMB patients are never handed the form.
If your team wants to work through ABN scenarios with real remits, the medical billing team runs this as part of onboarding, and our RCM training includes a Medicare liability module.
