A primary care practice ordered a vitamin D level on a 70-year-old with no qualifying diagnosis. Medicare denied it as not medically necessary, the lab billed the practice, and the practice tried to bill the patient. The patient, correctly, refused: nobody had told her in advance that Medicare might not pay. The practice absorbed the cost. Two weeks later the same practice made the opposite mistake, handing an ABN to every Medicare patient at check-in "just in case," which is prohibited. The question of when to use an ABN has a narrow, specific answer, and most practices sit on one side of it or the other.
The Advance Beneficiary Notice of Noncoverage, form CMS-R-131, is the written notice a provider gives an Original Medicare patient before furnishing a service that Medicare usually covers but is expected to deny in this instance, typically because it is not reasonable and necessary for this patient or exceeds a frequency limit. The patient reads why Medicare may not pay, sees the estimated cost, and chooses whether to receive the service and accept financial responsibility. With a valid ABN on file, the practice may bill the patient if Medicare denies. Without one, the practice may not.
A glossary line: "not reasonable and necessary" is Medicare's statutory standard for coverage. A service can be a covered benefit in general and still be denied for a specific patient because the diagnosis does not support it under a national or local coverage determination. That is the situation the ABN exists for. It is not for services Medicare never covers, and it is not for Medicare Advantage patients.
Key takeaways
- Use an ABN when a normally covered service is expected to be denied for this patient as not reasonable and necessary, or for exceeding a frequency limit.
- Do not use an ABN routinely, for statutorily excluded services, for emergencies, or with Medicare Advantage patients.
- The ABN must be given far enough in advance for the patient to decide, must list the specific service and a good-faith cost estimate, and must be signed and dated by the patient.
- Report modifier GA on the claim line when a valid ABN is on file, so the denial comes back as patient responsibility.
- The current form's approval date passed on January 31, 2026, and CMS has said to keep using it until a renewed version is released; watch for the new form.
When to use an ABN, and when it is prohibited
| Situation | ABN? | Why |
|---|---|---|
| Lab test ordered without a diagnosis covered under the applicable coverage determination | Yes | Covered service, expected denial as not reasonable and necessary for this patient |
| Screening test requested more often than Medicare's frequency limit (for example a second screening colonoscopy within the interval) | Yes | Frequency limitation is a valid ABN reason |
| Routine annual physical (99397) for a Medicare patient | No, but a voluntary notice is allowed | Statutorily excluded; Medicare never covers it, so the patient is liable regardless. A voluntary ABN may be used as a courtesy |
| Cosmetic procedure | No | Statutory exclusion; patient liable without notice |
| Every Medicare patient at check-in, as a blanket policy | Prohibited | Routine or "blanket" ABNs are not valid and violate Medicare's rules |
| Emergency or urgent situation | Prohibited | Notice given under duress is not valid |
| Medicare Advantage patient | No | The ABN is an Original Medicare form; request a pre-service organization determination from the plan instead |
| Service the provider is unsure about with no specific reason to expect denial | No | Generic uncertainty is not a permitted reason; you must have a specific, identifiable reason |
The "specific reason" test is the one to teach. Before handing over an ABN, the staff member should be able to write, in the reason box, why Medicare is expected to deny this service for this patient: "Medicare does not cover vitamin D testing for this diagnosis" or "Medicare covers this screening once every 24 months and the last one was 14 months ago." If nobody can write that sentence, an ABN is not appropriate.
How to complete the form so it holds up
The form has lettered blanks. Fill in the patient's name and identifier (not the Medicare number in full; the form allows an internal identifier), the specific items or services in plain language, the specific reason Medicare may not pay, and a good-faith estimated cost for each item. The estimate should be within reason of the actual charge; CMS guidance expects it to be within $100 or 25 percent of the actual cost, and an estimate that is far off can invalidate the notice.
The patient then chooses one of three options. Option 1: receive the service, have Medicare billed, and accept responsibility if Medicare denies (with appeal rights). Option 2: receive the service, pay now, and do not bill Medicare. Option 3: decline the service. The patient, not the staff member, must check the box. The patient signs and dates. The practice gives the patient a copy and keeps the original for at least five years from the date of service, or longer under state law.
Deliver it in person when possible, before the service, with time to ask questions. Telephone delivery followed by a mailed or electronic copy is allowed when in-person delivery isn't practical, and the conversation must be documented. Electronic ABNs on a tablet are acceptable if the patient can read and sign and receives a copy. A form handed to a patient already on the exam table for the procedure is not "in advance."
The claim side: GA, GX, GY and GZ
The ABN only works if the claim tells Medicare it exists. Append modifier GA to the line for the service covered by the ABN. Medicare then denies the line, if it denies, with a PR group code, patient responsibility, and the patient's Medicare Summary Notice tells them they owe it. Without GA, the denial comes back CO, provider liable, and you cannot bill the patient even with a signed ABN in the chart.
Modifier GZ means you expected the denial and did not obtain an ABN; Medicare denies with provider liability, and you have documented that you knew. Modifier GY is for statutorily excluded services, where an ABN is not required; it produces a denial the patient can take to a secondary insurer. Modifier GX indicates a voluntary ABN was given for a statutorily excluded service, and is used with GY. The four modifiers are a small language, and billers who know it stop losing patient balances to the wrong group code. Our billing team audits GA usage against ABN scans at least quarterly because the two drift apart whenever staff turn over.
The form version question in early 2026
The ABN form carries an expiration date from the Office of Management and Budget, and the current version's date was January 31, 2026. CMS has been working on a renewed form and has instructed providers to keep using the current version until the updated one is released and a transition date is announced. So as of this week, the form you have been using is the correct form. When CMS posts the renewed version, there is typically a period of some weeks in which either version is accepted, followed by a mandatory-use date. Put someone in charge of watching the CMS Beneficiary Notices Initiative page, and plan to swap the form in the EHR and at every front desk on the same day.
We think the version change is a good excuse to review how the form is actually used. Pull the last thirty ABNs in the chart. Check that each has a specific reason, a plausible cost estimate, a patient-selected option, a signature and a date before the service date, and a matching GA on the claim. In our experience the failure rate on that check is high the first time, and low after one training.
Questions we hear
Can we collect payment at the time of service when the patient chooses Option 1?
Yes. With Option 1 you bill Medicare, and you may collect from the patient in advance; if Medicare unexpectedly pays, you refund the patient promptly. With Option 2 the patient pays and Medicare is not billed at all, which removes their appeal rights, so most practices default to Option 1 unless the patient prefers otherwise.
What if the patient refuses to sign?
Document the refusal on the form, with a witness if possible, note the date and time, and then decide whether to furnish the service. If the service is furnished after a documented refusal to sign, the patient can still be held liable because notice was given. Many practices choose to defer the service instead, which is also permitted.
Does the lab need its own ABN, or does ours cover the test?
The ABN protects the entity that bills. If your practice draws the blood and an outside lab bills Medicare, the lab needs a valid ABN, and most labs will accept one obtained by the ordering practice on the lab's behalf if it names the lab or the test clearly. Coordinate with your reference lab on whose form is used and how it is transmitted.
What to do this week
- Pull the last thirty ABNs and check reason, cost estimate, option selected, signature date and matching GA modifier on the claim.
- Remove any blanket ABN from the check-in packet and replace it with a decision rule for when the form is offered.
- List the ten services your practice most often has denied as not reasonable and necessary and write the ABN reason sentence for each.
- Confirm no ABN has been used with a Medicare Advantage patient, and set up the pre-service determination process for those plans.
- Assign one person to watch for the renewed CMS-R-131 and plan the same-day swap.
