The 8-minute rule, and the other rule
Medicare counts units by total timed minutes across the visit: 8 to 22 minutes is one unit, 23 to 37 is two, 38 to 52 is three, and so on in 15-minute steps. Untimed codes such as evaluations, mechanical traction and unattended electrical stimulation are one unit each regardless of time and sit outside that total. A visit with 33 minutes of therapeutic exercise and 10 minutes of manual therapy is three timed units under Medicare, not four, and the third unit is assigned to the code with the most remaining minutes.
Many commercial payers do not follow Medicare here. They apply the AMA convention, where each timed code has to stand on its own with at least eight minutes, which can produce a different unit count for the identical visit. Applying one method to every payer overbills one group or underbills the other. We hold the counting method per payer and check units against documented minutes before submission.
Plans of care, certification and recertification
A Medicare plan of care has to be certified by the referring physician or non-physician practitioner, and recertified at least every 90 days or sooner if the plan changes. Claims for visits after the certification lapsed are technically for services without a valid plan, and that is how they are denied. Usually the cause is a signed order sitting in a fax queue at the referring office.
We track the certification date and the recertification due date on every Medicare and Medicare Advantage patient, send the recert request ahead of the deadline, and chase the signature. Where a signature arrives late, Medicare allows a delayed certification with a documented reason, and we assemble that rather than writing the visits off. Commercial plans have their own version of this in the form of prescription and referral requirements, which are tracked the same way.
KX modifier thresholds and the year-to-date ledger
Medicare no longer caps outpatient therapy, but it does set an annual dollar threshold for combined physical and speech therapy above which every claim line needs the KX modifier, attesting that the services are medically necessary and documented. A second, higher threshold triggers targeted medical review. The threshold applies to the patient across all providers, so a patient who spent the spring in a hospital outpatient department may cross it in your clinic at a visit that looks routine.
Adding KX to every line to be safe is not a solution; it is an attestation, and using it below the threshold or on maintenance care without skilled need is what medical review looks for. We pull the year-to-date therapy amount from the Medicare eligibility response, flag the patient as they approach the threshold, and confirm the documentation supports continued skilled care before KX goes on.
Visit limits and authorizations on commercial plans
Commercial plans typically cap therapy at an annual number of visits, often shared across physical, occupational and speech therapy and sometimes chiropractic as well. Many also authorize a set number of visits after the evaluation and require a progress report to extend it. The payer sees a counter ticking down, and the visit after the limit is denied as CO-119 with nothing to appeal.
The remaining visits and the authorization balance come from the eligibility check and go on the patient record, and the front desk can see both when scheduling. Reauthorization is requested with the progress note attached while visits remain. When visits run out, the self-pay conversation happens before the visit rather than in a statement later.
Physical therapy billing modifiers: GP, CQ, KX and 59
Every service under a physical therapy plan of care carries GP for Medicare and most commercial payers, and a missing GP is the simplest CO-4 there is. Services furnished in whole or in part by a physical therapist assistant carry CQ, which Medicare pays at a reduced rate, and the note has to show who did what minutes for the modifier to be applied correctly.
National Correct Coding Initiative edits pair several common therapy codes. Manual therapy billed with therapeutic activities, or an evaluation billed with treatment on the same day, is bundled unless modifier 59 or the appropriate X modifier is present and the note supports distinct services. We scrub every claim against the current NCCI table before it goes out.
- GP on every plan-of-care line; CQ where a PTA furnished the service
- KX applied only above the threshold and only with supporting documentation
- 59 or X modifiers applied to NCCI pairs when the note shows distinct services
Why therapy A/R needs its own approach
A physical therapy practice bills a high volume of low-dollar claims. A single denied unit is small, and the temptation is to leave it, but the same units denied across every visit of a twelve-visit episode is a meaningful amount and the pattern repeats with the next patient. Aging reports in therapy are read by denial reason and by payer rather than by balance, because that is the only view that shows a units-counting mismatch or a missing modifier as the single defect it is.
Denials are worked by CARC and RARC code, corrected claims go out in batches when the cause is systematic, and the cause is fixed at the point it started: the charge template, the eligibility workflow, or the plan-of-care tracking. A free A/R review is where we start, and a two- to four-week parallel run happens before anything switches.
