The KX modifier is a critical billing tool for suppliers providing therapeutic shoes and inserts under Medicare’s Therapeutic Shoes for Persons with Diabetes (TSPD) policy. When appended to a claim, the KX modifier signals to Medicare that all coverage criteria outlined in the Local Coverage Determination (LCD) and related policy article have been met, and documentation supporting medical necessity is on file. In other words, it is the supplier’s attestation that the patient qualifies for the benefit and that the claim is fully compliant.

For TSPD, coverage is limited to one pair of therapeutic shoes and up to three pairs of inserts or modifications per calendar year. To use the KX modifier correctly, suppliers must ensure that the patient has a diagnosis of diabetes and at least one qualifying condition such as neuropathy with callus formation, previous ulceration, foot deformity, poor circulation, or partial foot amputation. A certifying physician must manage the patient’s diabetes and provide written certification of medical necessity, supported by a face‑to‑face visit within six months prior to delivery. Only when these requirements are satisfied should the KX modifier be applied to the claim.

From a compliance perspective, the KX modifier is both a safeguard and a responsibility. Improper use-such as appending the modifier without complete documentation—can lead to claim denials, audits, or recoupment efforts. Suppliers must maintain thorough records that must be available upon request including physician certifications, fitting notes, and delivery documentation. Applying the KX modifier properly helps suppliers stay compliant.