A Medicare patient receives a service that Medicare later denies as not reasonable and necessary. Without a valid Advance Beneficiary Notice of Noncoverage, the practice typically cannot bill the patient for that service. The revenue is lost even though the care was delivered and documented. A single missing or defective notice can turn an expected patient payment into a write-off.
CMS released an updated version of Form CMS-R-131 in March 2026. The prior version could no longer be used after May 12, 2026. The current form is valid through March 31, 2029. For practice owners and billing managers, the form change is a timely reason to review how ABNs are issued, completed and reported on claims.
An ABN Shifts Liability Only When It Is Valid
The ABN transfers financial liability to an Original Medicare beneficiary when the practice expects Medicare to deny an item or service. That transfer applies only if the notice is delivered correctly and completed in full. The detailed requirements appear in Chapter 30 of the Medicare Claims Processing Manual. A defective notice is treated as if no notice were given.
Medical necessity is among the most frequent reasons medical claims get denied. The ABN is one of the few tools that preserves revenue after such a denial. It works only when every requirement is met before the service is furnished.
Most Defective ABNs Share the Same Errors
Billing reviews tend to find the same handful of errors across practices of every size and specialty. Each one can make an otherwise reasonable notice unenforceable.
| Mistake | Why It Invalidates the Notice | Correct Practice |
|---|---|---|
| Issuing it to a Medicare Advantage enrollee | The ABN applies only to Original Medicare | Request a pre-service organization determination from the plan |
| Using a routine or blanket notice | No specific reason for the expected denial is given | Issue the ABN only when denial is genuinely expected |
| Delivering it after the service begins | The patient has no time to make a decision | Deliver and explain the notice before the service |
| Leaving the noncoverage reason blank | The patient cannot understand the financial risk | State a specific reason for each item or service |
| Omitting the cost estimate | The patient cannot make an informed choice | Give a good-faith estimate within $100 or 25% of the actual cost |
| Preselecting an option | The choice must belong to the beneficiary | Let the patient select Option 1, 2 or 3 and sign |
| Using an outdated form | Only the current OMB-approved version is accepted | Use the CMS-R-131 version valid through March 31, 2029 |
Each of these errors produces the same outcome. If Medicare denies the service, the practice generally cannot collect from the patient. Most can be prevented with a short checklist reviewed at the time of scheduling.
Routine and Late Notices Are the Most Common Failures
Some practices ask every Medicare patient to sign an ABN as a precaution. CMS prohibits this approach. A notice issued without a specific reason to expect denial gives the beneficiary no meaningful information. A valid ABN identifies the particular item or service and explains why Medicare may not pay for it, such as a frequency limit or a diagnosis that does not meet coverage criteria.
Timing causes similar problems. The notice must be delivered far enough in advance for the patient to consider the options and ask questions. Presenting an ABN after a patient is gowned or after a specimen has been collected rarely meets that standard. ABNs are never used in emergency or urgent care situations.
Incomplete Fields Invalidate Otherwise Correct Notices
The CMS form instructions require specific entries in each section of the notice. The form must list the items or services, give a reason for expected noncoverage and include a good-faith cost estimate. Medicare numbers and Social Security numbers must not appear anywhere on the form. The beneficiary then chooses one of three options:
- Option 1: The patient receives the service, Medicare is billed and the patient pays if Medicare denies, with appeal rights preserved
- Option 2: The patient receives the service and pays directly, Medicare is not billed and no appeal is available
- Option 3: The patient declines the service and owes nothing
Staff must not preselect an option on the patient’s behalf. If a patient refuses to choose or sign, staff should annotate the notice to record the refusal and keep a copy on file. CMS expects practices to retain each ABN for five years from the date of service when no other requirement applies.
Claim Modifiers Must Match the Notice on File
An ABN protects the practice only when the claim reports it correctly. Medicare uses four HCPCS modifiers to identify liability notices. A mismatch between the modifier and the notice on file can shift liability back to the practice.
Modifier GA indicates that a required ABN was issued and is on file. GZ indicates that the practice expects a medical necessity denial but did not obtain an ABN, which leaves the practice liable. GX reports a voluntary ABN for a service Medicare never covers. GY reports a statutorily excluded service for which no notice was required.
These modifiers follow the same reporting logic as other modifiers in medical coding. Charge reviews should confirm that every GA line has a signed notice on file. A pattern of GZ lines often signals that the scheduling team is missing opportunities to issue valid notices.
Denied ABN Claims Still Require Follow-Up
When Medicare denies a claim billed with modifier GA, the patient receives a Medicare Summary Notice and becomes responsible for the balance. Patients who chose Option 1 keep their appeal rights. When Medicare pays a claim that the patient already paid, the practice must refund the amount collected beyond applicable cost sharing.
Clear communication at this stage prevents many patient billing disputes. A statement that references the signed ABN and the Medicare decision helps the patient understand the charge. Prompt follow-up also keeps these balances from aging into collections.
Denials on claims with a valid notice and denials caused by a defective one both deserve review. Dedicated denial management services group these outcomes by cause so recurring issues can be corrected at the scheduling stage. Those corrections reduce the number of write-offs tied to medical necessity.
Final Thoughts
A valid ABN converts an expected Medicare denial into a collectible patient balance. A defective one leaves the practice with the write-off. Medlife MBS reviews ABN workflows, confirms current form versions and checks modifier reporting before claims leave the practice. Through medical billing services that connect front-desk notices to claim submission, Medlife MBS protects revenue on every Medicare service. Contact the Medlife MBS team to schedule a review of current ABN processes.