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PT Billing: Units, Limits, and the Eight-Minute Rule

Timed-code unit calculation is the most common PT billing error, and it is systematic rather than occasional — so it repeats on every visit.

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2 min read · by White Glove Medical Billing
Evenly divided segments with one boundary slightly off

Physical therapy billing is arithmetic applied to documented time. When the arithmetic is wrong it is wrong the same way on every visit, which turns a small error into a systematic one.

Timed versus untimed

Some codes are billed per unit of time. Others are billed once per session regardless of duration. Mixing them up produces either lost revenue or overbilling, both consistently.

The unit calculation

Total timed minutes determine how many units may be billed, under a rule that sets thresholds for each additional unit. The complications are the parts practices skip: total timed minutes are summed across timed codes rather than counted per code, and untimed services are excluded from the total entirely.

Documentation must therefore record minutes per service, not a session length. A note saying "45 minutes" without a breakdown cannot support a unit calculation.

The other constraints

  • Visit and dollar limits. Plans cap therapy, and some caps are shared across disciplines — so occupational therapy can consume the physical therapy allowance.
  • Plan of care sign-off. Required, and required again at intervals. A lapse denies everything after it.
  • Discipline modifiers. Identify which therapy was delivered, and omitting them causes services to be combined against a shared limit.

The review worth doing

Take twenty recent visits and recalculate units from the documented minutes. If the numbers disagree with what was billed, the disagreement is almost certainly present on every visit and has been for as long as the process has run.

Denials Piling Up?

We handle the revenue cycle end to end — coding by certified coders, claim submission, denial management and appeals, and A/R follow-up, with six reported numbers every month.

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