Key takeaways
- Timed codes follow minutes, and untimed codes are billed once per session.
- GP, KX, and CQ are the modifiers most PT practices need to get right for Medicare.
- Track authorized visits so care does not continue past what the payer approved.
Physical therapy claims carry more detail than most. One visit can include several timed codes, untimed codes, modifiers for discipline and assistants, and authorization limits. Small errors repeat across many visits, so PT practices feel billing problems quickly.
Timed and untimed codes
PT services are billed with CPT codes that are either timed or untimed. Timed codes, such as therapeutic exercise and manual therapy, are billed in 15 minute units based on direct one on one time. Untimed codes, such as evaluations, are billed once per session regardless of length.
The 8 minute rule for Medicare
For Medicare and payers that follow CMS rules, units for timed codes are based on the total timed minutes in the visit. You need at least 8 minutes of timed service to bill one unit. Add up all timed minutes, divide by 15 for whole units, and add one more unit if 8 or more minutes remain. Some commercial payers use a different method, so check payer policy.
- Document start and end times or total minutes for each timed code.
- Do not count time for untimed services toward timed units.
- Make sure the units on the claim match the minutes in the note.
Modifiers that matter in PT
- GP: identifies services delivered under a physical therapy plan of care. Medicare requires it on therapy claims.
- KX: tells Medicare that services above the annual therapy threshold are medically necessary and supported by documentation. CMS updates the threshold each year.
- CQ: identifies services furnished in whole or in part by a physical therapist assistant, which can change Medicare payment.
- 59 or X modifiers: used when two services that normally bundle were truly separate, and only when documentation supports it.
Authorization and visit limits
Many commercial and Medicaid plans limit PT visits per year or require authorization after a set number of visits. Track authorized visits and dates, and request more before the patient runs out. A visit past the limit is often a denial nobody can fix after the fact.
Common PT billing errors
- Units that do not match documented minutes.
- Missing GP modifier, or KX missing once the threshold is reached.
- CQ not applied when an assistant provided the service.
- Visits beyond the authorized number or date range.
- Plan of care not certified or recertified on time for Medicare patients.
- Bundling edits, for example two codes billed without support for separate services.
Run a monthly check comparing billed units to documented minutes on a sample of visits. It is one of the fastest ways to catch errors before a payer does.
Where Afiable helps
Afiable bills PT claims with correct units, modifiers, and authorization checks, works denials, and follows up on AR, inside your current EHR. Book a free PT billing audit and we will review a sample of your claims and show you what to fix first.
Questions practices ask
Do commercial payers follow the 8 minute rule?
Some do and some use other methods, such as billing each code separately by its own minutes. Check each payer's policy.
Is the Medicare therapy threshold a hard cap?
No. Above the threshold, therapy can continue when it is medically necessary, documented, and billed with the KX modifier. Higher amounts may be reviewed.
This article is general information for practice owners and managers. Payer policies and regulations change, so confirm current rules with each payer before acting.