The 8-minute rule, and the units it costs you

What the rule does

Timed therapy codes are billed in 15-minute units, and the 8-minute rule decides how many units a given amount of time supports. Under Medicare the count runs on the TOTAL timed minutes in the visit, not on each code separately — at least 8 minutes for one unit, 23 for two, 38 for three, 53 for four, and so on in 15-minute steps.

In our experience the most common error is counting each code independently. Two codes at 10 minutes each is 20 total timed minutes, which supports one unit — not two.

Timed and untimed are counted differently

Service-based codes are billed once per session regardless of duration and do not enter the timed total. Mixing them into the count inflates units and produces exactly the pattern an audit looks for.

Not every payer follows it

Commercial payers may use a substantially different rule, most commonly one where each code is counted on its own with its own midpoint threshold. The same visit produces a different unit count under the two methods, legitimately.

[UNVERIFIED] Which rule a given commercial payer applies is a contract and policy question. Confirm it per payer rather than applying the Medicare method by default, because the difference is real money on every visit and neither method is wrong in general.

What the documentation has to carry

Total treatment time, time per timed code, and the skilled content of that time. A note recording units without minutes cannot support the units, and that is the finding rather than the arithmetic.

The other loss in therapy

Authorized visit units running out mid-plan. It is unappealable in most contracts because the service already happened, and it is entirely preventable by counting authorized units against visits delivered before the visit rather than after the denial.

Plan-of-care recertification dates are the same shape of problem: a date that passes quietly and denies everything after it.