KX

Overview

Modifier KX indicates that the supplier has documentation on file confirming the medical-necessity requirements specified in the relevant Local Coverage Determination (LCD) or Medicare Policy Article have been met. It is most heavily used in DMEPOS billing — affixing KX to a code certifies the supplier holds the standard written order, face-to-face evaluation note, and item-specific medical-necessity documentation required by the LCD. Without KX on codes where it is required, Medicare denies the claim as not meeting medical necessity. With KX, the claim passes the front-end edit, but the supplier remains subject to post-payment audit and must produce the documentation on demand.

When to use

• A DMEPOS LCD or Article explicitly lists KX as the required documentation indicator for the item being billed.
• All medical-necessity criteria in that LCD/Article are met and documented in the patient's file at the time of billing.
• A signed Standard Written Order (SWO) is on file before the supplier delivers the item.

Common mistakes

• Appending KX without first verifying the LCD lists KX as required for that specific code — KX is not a universal "documentation on file" modifier.
• Affixing KX before the documentation actually exists, on the assumption the physician's note will be obtained later. The documentation must exist at the time of billing.
• Using KX as a substitute for GA, GY, or GZ on items that should have an ABN modifier instead.

Examples

• E0601-KX — CPAP device delivered to a beneficiary with a documented in-lab sleep study, AHI ≥ 5, and signed compliance attestation from the treating physician.
• L1832-KX — Knee orthosis with adjustable joints delivered after a documented detailed written order and a face-to-face encounter establishing medical necessity for a brace with adjustable joints.