PostAcuteTools
Guide · Part B Therapy

The KX Threshold & Modifier

Outpatient therapy under Part B no longer has a hard dollar cap — but it does have an annual threshold, and once a patient crosses it, a single modifier decides whether the claim is paid or denied. Here’s how the thresholds and the KX modifier actually work.

In short

Each year, Medicare sets a KX modifier threshold on outpatient therapy spending per patient — one amount for PT and SLP combined, a separate one for OT. Below it, bill normally. Above it, you must append the KX modifier attesting medical necessity, or the claim is denied. A higher medical-review threshold ($3,000) sits above that, where claims can be selected for targeted review.

From a hard cap to a soft threshold

For two decades, Part B therapy had a hard cap — a dollar limit, after which Medicare simply stopped paying. The Bipartisan Budget Act of 2018 permanently repealed that cap and replaced it with a soft threshold: services above the line are still covered when they’re medically necessary, as long as the provider attests to that with the KX modifier.

1997Hard therapy cap createdby the Balanced Budget Act2018Hard cap repealed (BBA2018), replaced by the KXmodifier threshold2018–2028MR review threshold heldat $3,000
The hard cap stood for two decades before the Bipartisan Budget Act of 2018 turned it into a soft threshold backed by the KX modifier, keeping the targeted-review threshold separate.

The two thresholds

There are two lines to know. The first is the KX modifier threshold — the old cap amount, now just the point where the KX modifier becomes mandatory. The second, higher line is the medical-review (MR) threshold, fixed at $3,000 through 2028. Crossing it doesn’t change how you bill (you keep using KX), but it’s the point above which a claim can be pulled for targeted review.

KX threshold$2,480 · 2026MR threshold$3,000No modifier neededKX requiredKX + possible reviewcumulative therapy spending — per beneficiary, per calendar year →
Two lines, three zones. Below the KX threshold you bill normally; above it you must append the KX modifier or the claim is denied; above the medical-review (MR) threshold you keep using KX and the claim may be selected for targeted review.

PT + SLP share a threshold; OT is separate

The thresholds are tracked as two running tallies of a patient’s therapy spending for the year. Physical therapy and speech-language pathology count against one combined threshold; occupational therapy has its own. Both amounts are indexed annually by the Medicare Economic Index, so they drift up a little each year — the KX Threshold Tracker holds the current figures.

PT + SLPshare ONE combined thresholdPTSLPΣ$2,480 combined (2026)OThas its OWN separate thresholdOTOT$2,480 separate (2026)
There are two running tallies. Physical therapy and speech-language pathology share a single combined threshold; occupational therapy is tracked on its own. Each is indexed annually — the tracker holds the current figures.

What the KX modifier does

The KX modifier isn’t a formality. Above the threshold it’s required: it’s the provider’s attestation that the additional services are reasonable and necessary, and that the medical record backs that up. Submit a claim above the threshold without it and Medicare denies the claim; append it and medically necessary care keeps being paid.

97110Part B therapy serviceKXmodifier →The KX modifier is the provider’s attestation that the service is medically necessary and supported by documentation.Over threshold, KX missingDeniedOver threshold, KX appendedPaid
Above the threshold the KX modifier isn’t optional paperwork — it’s required. Without it, Medicare denies the claim; with it, medically necessary services keep being paid. (97110 shown as an example therapy code.)

Targeted medical review

The $3,000 MR threshold preserves a review process, but the key word is targeted: not every claim over $3,000 is reviewed. CMS’s review contractor selects claims based on patterns — things like unusually high billing, a high share of denied claims, or newly enrolled providers — rather than auditing everyone who crosses the line. Solid documentation is what carries a claim through if it is selected.

Key takeaways

  • The old hard cap is gone — repealed by the BBA of 2018 and replaced by a soft threshold.
  • Above the KX threshold, the KX modifier is required or the claim is denied.
  • PT + SLP share one threshold; OT has its own; both are indexed yearly.
  • The $3,000 MR threshold (through 2028) marks where claims may face targeted review.
  • The KX modifier is an attestation of medical necessity — backed by documentation.

Try it on the tools

KX Threshold Tracker →MPPR Calculator →Billing Units →Visit Estimator →

Last reviewed May 2026. Educational overview only — verify current threshold amounts and policy against the current CMS therapy services guidance and your MAC before billing.