What Is Modifier KX?
Modifier KX is a HCPCS Level II modifier appended to a claim line to attest that the documented medical-necessity requirements specified in the applicable Medicare LCD or NCD have been met, used for therapy services exceeding annual thresholds and for certain DME and laboratory services.
- PT, OT, and SLP practices serving Medicare patients should track threshold accumulation per beneficiary and appropriately apply Modifier KX once threshold is reached.
- Documentation in the plan of care should explicitly tie continued treatment to functional goals and medical necessity per the relevant LCD.
Modifier KX
Also known as: KX Modifier; Requirements Specified in the Medical Policy Met
Modifier KX is a HCPCS Level II modifier appended to a claim line to attest that the documented medical-necessity requirements specified in the applicable Medicare LCD or NCD have been met, used for therapy services exceeding annual thresholds and for certain DME and laboratory services.
Definition
Most prominently used to flag therapy services (PT, OT, SLP) exceeding the Medicare annual therapy threshold ($2,480 for CY 2026 for PT and SLP services combined, plus a separate $2,480 for OT services). After threshold, Modifier KX attests that services remain medically necessary per LCD-defined criteria. Above an additional 'targeted medical review' threshold ($3,000 for CY 2026, held at that amount each calendar year until 2028 and indexed to the Medicare Economic Index thereafter), claims may be selected for review. Modifier KX is also used for various DME (e.g., CPAP, hospital beds), continuous glucose monitors, and certain lab services to confirm coverage criteria are met. Inappropriate use of KX without documentation is a top OIG audit risk.
Example
A PT patient has accumulated $2,500 in PT services year-to-date in 2026, crossing the $2,480 CY 2026 PT/SLP threshold. The next PT visit (CPT 97110) bills with Modifier KX appended to attest that continued therapy is medically necessary per the Medicare therapy LCD criteria. Without KX, the claim denies for exceeding the threshold; with KX but lacking documentation, the claim is at audit risk.
Common Misconceptions
Modifier KX is not a 'bypass' modifier — it is a sworn attestation that documentation supports continued medical necessity. The therapy threshold is no longer a hard cap (post-BBA 2018), but documentation must support the necessity for services above the threshold.
Practical Application
PT, OT, and SLP practices serving Medicare patients should track threshold accumulation per beneficiary and appropriately apply Modifier KX once threshold is reached. Documentation in the plan of care should explicitly tie continued treatment to functional goals and medical necessity per the relevant LCD.
Related Terms
LCD / NCD (Local & National Coverage Determinations)
An NCD is a nationwide CMS coverage policy specifying whether Medicare will cover a service; an LCD is a coverage policy issued by a Medicare Administrative Contractor (MAC) for its jurisdiction when no NCD applies, defining medical necessity criteria and covered diagnosis codes.
Read definitionCPT (Current Procedural Terminology)
CPT is the five-digit procedural code set developed and maintained by the American Medical Association that describes medical, surgical, and diagnostic services performed by physicians and qualified health professionals; it is HIPAA-named for use in claims.
Read definitionCARC 50
CARC 50 is the X12 claim adjustment reason code a payer returns when it has determined that a service does not meet its coverage criteria for medical necessity — a Medicare local or national coverage determination, or a commercial plan’s own medical policy.
Read definitionWhere This Applies on MedPrecision
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