ABNs and the GA, GX, GY, GZ Modifiers in Therapy

An Advance Beneficiary Notice of Noncoverage (ABN), Form CMS-R-131, is issued before furnishing a service Original Medicare is expected to deny, so the patient can decide in writing whether to pay out of pocket. CMS’s FFS ABN page describes it as issued “in situations where Medicare payment is expected to be denied,” to “transfer potential financial liability to the Medicare beneficiary,” under Section 1879 of the Social Security Act (Medicare Claims Processing Manual, Ch. 30).

Therapy practices meet the ABN in two situations, and mixing them up is where errors start. A patient who has met goals, plateaued without a skilled need, or no longer needs care that is reasonable and necessary requires a mandatory ABN, regardless of dollar amount. A service Medicare never covers, such as a wellness class, only calls for a voluntary notice as a courtesy. Which one applies, and which of the four claim modifiers, GA, GX, GY, or GZ, goes on the line, decides who is liable and what the remittance shows.

The CY 2026 KX modifier threshold is $2,480 for PT and SLP services combined and $2,480 for OT services, per CMS Transmittal R13437CP, with a separate $3,000 medical review threshold per the CMS Therapy Services page. Crossing either threshold does not, by itself, justify an ABN. This guide works from CMS manuals, transmittals, the ABN form, and MAC guidance on the March 2026 form revision. Current as of September 2026.

What an ABN is, who issues it, and what it does

The ABN is issued by “providers (including independent laboratories, home health agencies, and hospices), physicians, practitioners, and suppliers” enrolled in Original Medicare, per the CMS FFS ABN page. Its function is a liability shift: without a valid ABN, a provider who furnishes a service Medicare denies as not reasonable and necessary generally cannot bill the patient. With a valid ABN, liability moves to the beneficiary under Section 1879 and 42 CFR 411.404 and 411.408, the authorities the form’s own disclosure statement cites.

Two limits matter for therapy. Ch. 30, §50.1 is explicit: “the ABN is given to beneficiaries enrolled in the Medicare FFS program. It is not used for items or services provided under the Medicare Advantage (MA) Program or for prescription drugs provided under the Medicare Prescription Drug Program (Part D).” MA members are outside this process entirely, and except for DME suppliers, only enrolled providers and suppliers can issue an ABN.

Mandatory vs. voluntary: which applies in therapy

Ch. 30, §50.2 lists the provisions that make an ABN mandatory, led by “§1862(a)(1) of the Act (not reasonable and necessary).” Ch. 5, §10.5 spells out the therapy trigger: “At the time the clinician determines that skilled services are not necessary, the clinical goals have been met, or there is no longer potential for the rehabilitation of health and/or function in a reasonable time, the beneficiary should be informed,” and the ABN must be issued before that next service if the patient wants to continue anyway.

That covers the three situations therapy sees most: goals met, a plateau where the skilled component is gone (the manual’s trigger is the point where “skilled services are not necessary,” so maintenance care that still requires a therapist’s skills is a different question), and care no longer reasonable and necessary. Dollar amount is irrelevant in all three. Ch. 30, §50.2.1 contrasts this with statutorily excluded, never-covered care: “ABNs are not required for care that is either statutorily excluded from coverage under Medicare… However, CMS strongly encourage healthcare providers and suppliers to issue the ABN for care that is never covered.” CMS’s example: a patient discharged from PT after reaching her goals who then pays out of pocket for Tai Chi wellness classes her PT offers the community (2018 therapy ABN FAQ). That was never a Medicare benefit, so no mandatory notice applies.

For a voluntary notice, §50.2.1 says “the beneficiary should not be asked to choose an option box or sign the notice,” and MLN006266 adds “issuing the notice voluntarily doesn’t affect financial liability.” It’s a courtesy, not a document with mandatory-ABN execution requirements.

How the ABN interacts with the KX threshold

Crossing $2,480 does not, by itself, justify a mandatory ABN. CMS’s 2018 therapy ABN FAQ is direct: “Medicare covers therapy services above the -KX modifier thresholds for which the therapist or therapy provider attests are medically reasonable and necessary,” and the same applies to the $3,000 MR threshold. Above either figure, the beneficiary owes only the usual copay and deductible on covered care; see the KX threshold guide for how the threshold itself works.

What actually triggers the mandatory ABN is a necessity determination, independent of dollar amount. Providers “are required to issue the ABN… prior to providing therapy that is or may be denied as not medically reasonable and necessary regardless of the amount of incurred expenses.” CMS’s own worked example makes the point with a number well below the threshold: a patient with $630 of incurred expenses who has met their goals and wants to continue weekly still needs an ABN first; the trigger is the necessity decision, not the balance against $2,480.

Two modifier rules follow. KX and GA cannot go on the same claim line: the FAQ and Noridian JF Part B both call them “opposing payer policy,” since KX attests necessity while GA flags a possible denial. And a claim denied solely for a missing KX modifier above the threshold is provider liability under §1833(g)(8) per the same FAQ, not something an ABN can retroactively fix.

CMS does allow a voluntary notice once a patient is above the threshold, even for care excepted from the cap (Ch. 5, §10.5), with no option box or signature required. Not permitted: treating the threshold as a trigger for blanket notices. Noridian is explicit that “providers/suppliers must not issue an ABN to all beneficiaries who receive services exceeding yearly threshold amount.”

GA, GX, GY, GZ: the modifier decision table

Each modifier tells the contractor a different story about notice and necessity, and produces a different remittance. Definitions: MLN006266; liability and remittance: Ch. 1, §60.4.2 and §60.5.

GA doesn’t automatically deny the line; §110.5.1 treats it as a “rebuttable administrative presumption” that a valid ABN exists, and the manual’s note ahead of §30.3 says that if the notice is found invalid “the contractor will override the GA code” and hold the provider liable. GX and GY lines are submitted already expecting denial (Ch. 1, §60.4.2). GZ has been auto-denied without complex medical review since Transmittal R2148CP took effect July 1, 2011.

Which modifier to use:

• Mandatory ABN signed, patient chose Option 1: GA
• Never-covered service, voluntary ABN issued: GX with GY on the same line
• Never-covered service, no notice at all: GY alone
• Not reasonable and necessary, no ABN issued: GZ

Combination rules, from CMS Transmittal R1921CP: GX may pair with GY on one line. GX cannot combine with GA or GZ; Medicare systems “return the claim to the provider” if it sees that pairing. KX and GA still cannot share a line, per above.

Patient options and money outcomes

The ABN Form Instructions define three options on a mandatory ABN, and the patient chooses only one:

• Option 1: gets the service, provider must submit the claim to Medicare, producing an appealable payment decision. This is the GA line.
• Option 2: gets the service, pays out of pocket; no claim filed, no appeal rights.
• Option 3: declines the service; nothing furnished, nothing billed.

Choosing Option 2 does not violate mandatory claim submission rules: Ch. 30, §50.17.A is explicit that a claim withheld “at the beneficiary’s request by their choice of Option 2” is not a violation, though the beneficiary can still ask for the claim later.

Once a valid ABN is signed, Ch. 30, §50.9.A allows billing “the healthcare provider or supplier’s usual and customary fee,” not the fee schedule amount, and §50.15 allows collecting “immediately after an ABN is signed.” Skip a required ABN, or issue an invalid one, and the provider “is precluded from collecting funds from the beneficiary and is required to make prompt refunds if funds were previously collected.” If Medicare later pays after you’ve already collected, MLN006266 sets the clock: refunds are timely within 30 days of the remittance advice, or 15 days after an appeal determination.

Dual-eligible patients (QMB or Medicaid) must select Option 1, and “the provider can’t bill the dual eligible beneficiary when the ABN is delivered… Providers must not bill the patient until adjudication by both Medicare and Medicaid” (instructions). And MLN006266 bars using an ABN to shift liability for a Medically Unlikely Edit denial, a patient’s share of a bundled payment, or care Medicare otherwise fully covers, or to compel patients “in a medical emergency or under great duress.”

Execution errors that void the ABN

An ABN that looks complete can still be invalid, per Ch. 30, §40.2.2 and the ABN Form Instructions:

• Routine, generic, or blanket notices. No “specific, identifiable reason to believe Medicare will not pay,” or issuing to every patient regardless of circumstance, doesn’t protect the notifier.
• Signed-blank notices. A signature on a blank form, completed later, is invalid.
• Pre-selected options. Pre-selecting an option “invalidates the notice”; the signature line “can’t be completed in advance.”
• Missing reason or cost estimate. Every item needs an applicable reason and a good-faith estimate; a missing one voids the line.
• Late issuance. An ABN delivered after non-covered care starts cannot be backdated; the provider is liable for care furnished before delivery.
• A new ABN is required whenever care, health status, or coverage guidelines change; otherwise one ABN can cover a repetitive course of treatment.
• Refusal to sign. Annotate the original, list a witness if available, and generally don’t furnish the service unless withholding it creates a safety concern.
• Delivery and explanation. Far enough in advance to weigh the options, explained in full.
• Wrong form version. §50.5.B requires the current version “exclusively”; an expired form can create liability on its own.
• No MBI or SSN on the notice.
• Retention: 5 years from discharge or completion of care; electronic retention is acceptable.
• Remote/electronic delivery is allowed (phone, mail, secure fax, email) if a phone contact is followed immediately by a written copy.

The 2026 form revision

Form CMS-R-131 was updated in 2026. Per Noridian JF Part B, OMB approved the current version on March 13, 2026, and the prior version stayed valid only through May 12, 2026. The form footer now reads “Form CMS-R-131 (Exp. 03/31/2029),” the only version your practice should be handing patients as of September 2026.

Beyond the expiration date, the ABN Form Instructions describe plain-language changes “for improved usability and reduced burden for notifiers”: the table headers now read “Item, test, service or care,” “Reason Medicare may not pay,” and “Estimated cost,” and Option 1 now opens “I want the item, test, service or care listed above, and I want Medicare to be billed for an official decision on payment…” Clear any cached PDF of the old form from a shared drive or portal.

A workflow that handles this

1. Check accrual against the threshold as you document, so you know where a patient sits relative to $2,480 before a necessity conversation is needed.
2. Decide necessity at each reassessment: goals met, plateau without a skilled component, or still reasonable and necessary. That decision, not the dollar figure, triggers the mandatory ABN.
3. Issue the ABN before the next visit, never at or after service, with a specific reason and a good-faith cost estimate.
4. Pick the modifier from the option chosen: GA for Option 1, no claim for Option 2, nothing to bill for Option 3.

Quick answers

Does an ABN apply to Medicare Advantage patients? No, the Section 1879 process is for Original Medicare fee-for-service only.

Does crossing the $2,480 KX threshold require an ABN? No. The mandatory trigger is a necessity determination, independent of dollar amount.

Can KX and GA go on the same claim line? No, they convey opposing positions and cannot appear together.

What happens if I bill GZ instead of GA? The line auto-denies with the provider liable (Group Code CO, CARC 50), since GZ signals no ABN for an expected necessity denial.

Do I need a signature for a voluntary ABN? No. For never-covered services, the beneficiary shouldn’t be asked to choose an option or sign.

Can I bill a dual-eligible patient right after they sign an ABN? No. Billing waits until both Medicare and Medicaid have adjudicated.

Which ABN version should I use now? The version expiring 03/31/2029, effective since March 13, 2026; the prior version stopped being valid after May 12, 2026.

None of this changes because a system tracks it, but tracking it changes when the conversation happens. PrismEHR tracks accrued therapy expenses per beneficiary against the KX modifier threshold as claims are documented, and lets organizations define their own billing rules, including minute and unit restrictions, enforced at the point of documentation and reinforced at claim creation. Knowing where a patient sits against $2,480 as you document is what turns “is this still necessary” into a conversation before the visit, not a question the remittance asks for you. See the KX threshold guide for the accrual mechanics, and how it fits physical therapy practices.