What the KX modifier means on a therapy claim
The KX modifier is the attestation a therapy provider adds to Medicare claims once a patient's outpatient therapy spending for the year passes the KX modifier threshold. By appending it, the provider confirms that the services are reasonable and necessary, require the skills of a therapist, and are supported by documentation in the medical record.
KX does not add benefits by itself. It is a statement of medical necessity, and Medicare claims for services above the threshold that lack it are denied. The modifier matters for every physical therapy, occupational therapy and speech-language pathology practice that treats traditional Medicare patients.
From therapy caps to the KX threshold
Medicare once applied hard annual caps to outpatient therapy, with an exceptions process for patients who needed more care. Section 50202 of the Bipartisan Budget Act of 2018 repealed the caps and kept the dollar amounts as thresholds instead. Above them, care continues to be covered when it is medically necessary and the KX modifier is applied.
The same law kept a separate, higher targeted medical review threshold. Claims above that second level may be selected for review, but CMS states that not every claim over it is reviewed. Reviews are targeted using factors such as billing patterns.
How the KX modifier threshold works
There are two separate thresholds per beneficiary per calendar year. Physical therapy and speech-language pathology share one combined amount; occupational therapy has its own.
For 2026, CMS set the KX threshold at $2,480 for physical therapy and speech-language pathology combined, and a separate $2,480 for occupational therapy (CMS Transmittal R13437CP, issued October 30, 2025). CMS updates these amounts each calendar year, so confirm the current figure on CMS’s Therapy Services page before applying it to a new year.
| Item | How it works |
|---|---|
| PT and SLP threshold | One combined amount for physical therapy and speech-language pathology services in a calendar year |
| OT threshold | A separate amount for occupational therapy services |
| What counts toward it | The Medicare allowed amount for outpatient therapy services, including the patient's cost sharing, not the billed charge |
| Whose services count | Therapy from all outpatient settings and providers during the year, not only your practice |
| Reset | Each January 1 |
| Above the threshold | Add KX to claim lines when the services are medically necessary; claims without it are denied |
| Targeted medical review | A higher, separate level at which claims may be selected for review |
Because services from other providers count, a new patient may arrive with part of the year's threshold already used. Check the patient's year-to-date therapy amounts through the Medicare eligibility response or your Medicare Administrative Contractor's portal at intake.
The KX modifier threshold 2026: where to find the amount
CMS sets the KX modifier threshold for 2026, as it does every year, in the Medicare Physician Fee Schedule final rule, and posts the current figures on its Therapy Services web page. The amount is indexed annually by the Medicare Economic Index, so it usually changes a little each January.
This article does not quote the dollar figure because it changes yearly and should always be taken from the source. To confirm the current amount:
- Open the CMS Therapy Services page, which lists the current PT/SLP and OT thresholds.
- Cross-check the Physician Fee Schedule final rule or the CMS fact sheet for that year.
- Look for the MLN Matters article or change request titled Annual Update of Per-Beneficiary Threshold Amounts.
- Update the threshold in your practice management system's alert or tracking report before the first claims of the year go out.
The targeted medical review threshold is set separately under the same law. Read it from the same CMS page rather than assuming it moves in step with the KX amount.
Using the KX modifier in physical therapy, OT and SLP
For KX modifier physical therapy billing, the practical work happens at charge entry. The modifier goes on the claim lines for services that exceed the threshold, together with the discipline modifier that every Medicare therapy line already needs.
| Modifier | Meaning | When it appears |
|---|---|---|
| GP | Services delivered under an outpatient physical therapy plan of care | Every PT line |
| GO | Services delivered under an outpatient occupational therapy plan of care | Every OT line |
| GN | Services delivered under an outpatient speech-language pathology plan of care | Every SLP line |
| KX | Requirements specified in the medical policy have been met | Lines above the threshold, when medically necessary |
| CQ / CO | Service furnished in whole or in part by a PT assistant / OT assistant | Assistant services meeting CMS criteria |
On an institutional claim, CMS instructs providers to place KX on all lines that refer to the same threshold once any line on the claim exceeds it. Follow your Medicare Administrative Contractor's instructions for professional claims, and keep the GP, GO or GN modifier on every line.
Do not add KX automatically for every patient with a given diagnosis. CMS warns that routine use of KX will look aberrant in data analysis and invite review. Apply it case by case after confirming the documentation supports continued skilled care.
Documentation that supports KX
KX is a promise that the record backs up the claim. CMS lists therapy claims billed with KX as an approved Recovery Audit Contractor review topic, which makes documentation the main defense.
- A current, certified plan of care with functional goals.
- Progress reports showing measurable change or the need for skilled maintenance.
- Daily notes with timed minutes that match billed units under the 8-minute rule.
- Clear reasons why the patient needs skilled therapy rather than a home program.
- Re-certification signed within the required timeframe.
If a service is not medically necessary, KX is not the right tool. Consider whether an Advance Beneficiary Notice of Noncoverage (ABN) is appropriate before the service is provided, following CMS ABN instructions.
Tracking the threshold in a busy clinic
Most KX problems are tracking problems. A simple routine keeps claims from being denied for a missing modifier or flagged for an unnecessary one.
- At intake, check the patient's year-to-date therapy amounts for PT/SLP and OT.
- Set an alert in your practice management system as the running total approaches the threshold.
- Have the treating therapist confirm medical necessity before KX is added.
- Review denials for missing KX and correct and resubmit promptly.
- Watch patients approaching the targeted medical review level, and audit their records first.
Medicare Advantage plans set their own visit limits and authorization rules, so the KX process applies mainly to traditional Medicare. Check each plan's policy. Our physical therapy billing guide covers the wider PT claim workflow.
Support for therapy claims
Fastora's certified coders review therapy modifiers, threshold tracking and documentation for physical therapy and rehab practices as part of denial management and claims work. A free billing assessment can show where KX or therapy-modifier denials are slowing payment.
What is the Medicare KX modifier?
The Medicare KX modifier is appended to therapy CPT codes to confirm the services are medically necessary and to request an exception to the therapy cap threshold when it applies. It tells Medicare the claim should process even though the beneficiary is over the KX threshold amount for the year.
When should you use the KX modifier?
Use the KX modifier when therapy services are medically necessary and the patient has exceeded the annual therapy threshold. Do not append it routinely on every claim below the threshold — misuse is a known audit trigger. The note must support medical necessity for every date of service carrying the modifier.
Checklist
Frequently asked questions
What happens if I forget the KX modifier above the threshold?
Medicare denies claims for therapy services above the threshold that are submitted without KX. If the services were medically necessary and documented, correct the claim with the modifier and resubmit following your Medicare Administrative Contractor's corrected claim process.
Is the KX threshold a hard limit on therapy?
No. Since the 2018 repeal of the therapy caps, there is no hard limit for medically necessary outpatient therapy. The threshold is the point at which the KX attestation is required, and a separate higher level may trigger targeted medical review.
Do PT and OT share one threshold?
No. Physical therapy and speech-language pathology share a combined threshold, and occupational therapy has a separate one. A patient receiving both PT and OT can approach each threshold independently.
Do Medicare Advantage plans use the KX modifier?
Some do and some do not. Medicare Advantage plans can set their own visit limits, authorization rules and modifier requirements, so check the plan's provider manual or your contract rather than assuming traditional Medicare rules apply.
