Physical therapy billing services from evaluation to visit cap

Physical therapy billing runs on 15-minute units: timed CPT codes bill by minutes under the 8-minute rule, untimed codes bill once per session, and Medicare caps the year with a therapy threshold that the KX modifier extends. The unit math decides whether a session is paid correctly, and the caps decide whether visits late in a plan of care are paid at all. Flexbone runs the benefit checks, the authorization and visit-cap tracking, and the denial work that keep delivered therapy visits billable.

How does the 8-minute rule work in physical therapy billing?

Timed codes bill in 15-minute units, and Medicare pays a unit once at least 8 minutes of that service were provided. The timed codes are the hands-on ones: therapeutic exercise (97110), neuromuscular re-education (97112), manual therapy (97140), and therapeutic activities (97530). Total timed minutes across the session set the total units: 8 to 22 minutes is one unit, 23 to 37 is two, 38 to 52 is three. Untimed codes bill once per session regardless of duration, and they include the evaluation codes 97161 through 97163 and supervised modalities such as hot and cold packs (97010). Commercial payers vary: some follow the Medicare method and others pay a unit per code, so the rule set is per payer, not per clinic. The physical therapy billing explainer works through the unit math with examples.

How do visit caps and the KX modifier work?

Medicare replaced its hard therapy caps with an annual dollar threshold in 2018. Claims above the threshold must carry the KX modifier, which attests that the continued care is medically necessary and documented. Billing above the threshold without KX denies, and appending KX without supporting documentation creates audit exposure. Commercial plans manage the same risk with visit caps instead: a set number of visits per year or per condition, authorization tied to the plan of care, and reauthorization required to continue. A visit delivered past the authorized count is usually not payable, which makes visit tracking a scheduling problem as much as a billing one. The post on AI scheduling for physical therapy covers the scheduling side of cap tracking.

Why do physical therapy claims deny?

Therapy denials are concentrated and mechanical. A lapsed plan-of-care certification, because the physician signature or recertification date passed. A visit delivered past the authorized count, or above the Medicare threshold without KX. A missing therapy modifier, such as GP, that identifies the discipline. Unit counts that disagree with the documented minutes under the 8-minute rule. Each of these is checkable before submission. Flexbone runs the therapy benefit check up front, reading visit limits and used counts where the payer 271 response reports them, tracks visits against the cap, and flags claims whose units or modifiers disagree with the record before they file. Denials that still arrive are mapped by CARC code, corrected, and resubmitted, with appeals assembled for the medical necessity disputes.

How does Flexbone run physical therapy billing?

Flexbone deploys browser and voice agents inside your therapy EHR and billing system. Agents verify the therapy benefit and visit limits before the evaluation, submit the plan-of-care authorization and the reauthorization before the cap is reached, review units and modifiers pre-submission, and work the denial queue. The scheduling and adherence side, the recurring visit series and reminder cadence a plan of care depends on, is covered on the AI for physical therapy page. Results write back to the chart with an audit trail, and exceptions route to your billers with context.