Co-Treatment Billing: PT and OT Under Medicare Part B

When a physical therapist and an occupational therapist work with the same patient at the same time (a transfer, a functional mobility task, a seating adjustment), Medicare Part B does not let both disciplines bill their own full set of minutes for it. CMS’s “11 Part B Billing Scenarios for PTs and OTs” FAQ, reviewed September 2009 and still hosted by CMS (the same Part B language is reproduced verbatim in the October 2026 RAI Manual), states it plainly: “only one therapist can bill for the entire service or the PT and OT can divide the service units.” Not both billing the same minutes, and not each discipline billing whatever time it wants.

That arithmetic trips up multidisciplinary clinics constantly, especially practices with staff who came from skilled nursing, where Part A co-treatment runs on different rules entirely. Split a 40-minute co-treatment session evenly (20 minutes PT, 20 minutes OT) and the two disciplines bill 2 units total, not the 3 units a single discipline would bill for the same 40 minutes, because each half rounds down to one unit on its own. Add a PTA or OTA and CQ/CO stack on top of the split. Add a same-day evaluation from each discipline and NCCI edits come into play, though not the ones most practices assume are active.

This guide works from the primary sources: the CMS Part B billing scenarios FAQ, the Medicare Claims Processing Manual (Pub. 100-04, Ch. 5), the Medicare Benefit Policy Manual (Pub. 100-02, Ch. 15), the CY 2026 RAI Manual, and the current NCCI Policy Manual and practitioner PTP edit file. Current as of September 2026.

Can a PT and an OT bill for the same time under Medicare Part B?

CMS’s 11 Part B Billing Scenarios document (reviewed 9/2009) answers this in Scenario 4, “Team Therapy”: “Where a physical and occupational therapist both provide services to one patient at the same time, only one therapist can bill for the entire service or the PT and OT can divide the service units.” CMS’s own example: a PT and an OT work together for 30 minutes on transfer activities. Either they each bill one unit of 97530 (2 units, divided), or one discipline bills both units and the other bills nothing. Both disciplines separately billing the full 30 minutes is not allowed. The same rule applies within one discipline: two therapy assistants treating the same patient at once can split the units, “billed by the supervising therapist(s).”

The underlying principle sits in the Medicare Claims Processing Manual, Ch. 5, §20.3: “The time counted is the time the patient is treated.” CMS’s example there is gait training that needs both a therapist and an assistant in the parallel bars: “each 15 minutes the patient is being treated can count as only one unit of code 97116.” Two clinicians in the room does not mean two units; the clock runs on the patient, not per provider, which is exactly why co-treatment forces a split rather than doubling. See our 8-minute rule guide for the minute-to-unit mechanics.

How do you split minutes when a PT and OT co-treat?

The unit chart from CPM §20.2.C still applies to each discipline’s timed minutes once the total can’t be double-counted:

Example 1: full co-treatment, 40 minutes, split evenly. A PT and an OT are both present the entire session. The PT works on sit-to-stand and transfer training (97530); the OT works on upper-body dressing during the same activity (97535). They divide the time 20/20.

That’s 2 units for a 40-minute session. A single therapist treating the same patient alone for 40 minutes would bill 3 units (38-52 range). The even split costs a unit, because 20 minutes individually rounds down to one unit for each discipline rather than pooling into a higher bracket.

Scenario 4 permits other divisions of the same 40 minutes: the PT could document 25 minutes (2 units of 97530 GP) and the OT 15 (1 unit of 97535 GO), for 3 units total, or one discipline could bill the entire 40 minutes (3 units) while the other documents zero billable minutes. Not permitted: each discipline billing the full 40 minutes separately (3 units apiece, 6 units total for 40 minutes of patient time). No combination of documented minutes across both notes may exceed the minutes the patient was actually treated.

Example 2: partial overlap. A PT sees the patient for 45 minutes: 30 minutes alone (97110, 15 minutes; 97116, 15 minutes), then the OT joins for the final 15 minutes for functional transfers (PT continues on 97530, OT works 97535 concurrently).

Both options total 3 units for the 45-minute visit. Under Option B, the OT’s note still records the co-treatment and goals addressed, with zero billable minutes. Not permitted: the PT billing the full 45 minutes (3 units) while the OT also bills its 15 overlap minutes (1 unit), for 4 units total, since that double-counts the 15 minutes both clinicians were present.

What if a PTA or OTA is one of the co-treating providers?

CQ (PTA) and CO (OTA) apply whenever an assistant furnishes more than 10 percent of a unit, per CMS’s billing examples for CQ/CO: “services furnished by the PT together with the PTA or by the OT together with the OTA are considered to be performed by the PT/OT,” while “services or minutes/portions of services performed by the PTA/OTA are independent of those performed by the PT/OT.” That “together” language is written for a PT with its own PTA, or an OT with its own OTA, same discipline. As a plain reading, it does not convert a PTA’s minutes into therapist minutes just because an OT is co-treating in the room, and Scenario 4 already says assistant units can be split “and billed by the supervising therapist(s)” of each discipline.

Example 3: a PTA co-treats with an OT, 30 minutes, split 15/15. The PTA furnishes 97110 under the PT plan of care; the OT furnishes 97535.

The PT line carries CQ because the PTA furnished the entire unit and no PT was present to invoke the “together” exception; the OT line carries no CO, since an OT furnished it. Flip the roles and an OTA with a PT bills GO and CO on the OT line, GP with no CQ on the PT line. If both assistants co-treat, each supervising therapist bills its own line with its own modifier: CQ on the PT/PTA line, CO on the OT/OTA line.

Those modified lines pay 85 percent of the otherwise-applicable amount; see our CQ/CO modifier guide for the arithmetic and the 10 percent standard’s exceptions. Since January 1, 2025, PTAs and OTAs in private practice need only general supervision, not on-site; see our PTA/OTA supervision guide for what changed.

Can a PT and an OT both bill an evaluation on the same day?

Yes, when a different practitioner performs each evaluation. NCCI Policy Manual, Chapter XI, §P.1 (Revision Date 1/1/2026): “A physician or facility shall not report both an occupational therapy evaluation/re-evaluation service and physical therapy evaluation/re-evaluation service if performed by the same practitioner. If the 2 services are performed by 2 different practitioners on the same date of service, both procedures may be reported.” A PT evaluation (97161-97164) and an OT evaluation (97165-97168), by their own disciplines, are both billable the same day.

Practices often assume there’s a current PT/OT evaluation pair needing a modifier, and there isn’t one. The practitioner PTP edit file (v323r0, effective October 1, 2026) shows a pairing between 97161-97163 and 97165-97168, and between 97164 and 97165-97168, but both carry an effective date of 2017-01-01 and a deletion date of 2017-06-30. That edit existed for six months in 2017 and hasn’t been active since; there is no current NCCI edit pairing a PT evaluation with an OT evaluation.

What is active: 97535 (OT self-care/home management) as Column 1 against 97164 (PT re-evaluation) and 97168 (OT re-evaluation), both effective October 1, 2020, with no deletion date. So a PT re-evaluation billed the same day as an OT’s 97535 hits a live edit with modifier indicator 1 (may bypass under appropriate circumstances): per NCCI Chapter XI, §P.3, a re-evaluation “shall not be routinely reported during a planned course of physical or occupational therapy,” and only when the patient’s status has changed and the re-evaluation is medically reasonable and necessary may the 97164 line carry modifier 59 or XU, with documentation of that change. Per NCCI Chapter I, §E, “a modifier shall not be appended to a HCPCS/CPT code solely to bypass an NCCI PTP edit if the clinical circumstances do not justify its use.” See our NCCI edits guide for the full therapy PTP pair list.

Same day, not co-treating: separate plans of care, MPPR, and the KX split

Not every same-day PT and OT visit is co-treatment. Example 4: a PT sees the patient at 9:00 a.m. for 40 minutes (97110, 25 minutes; 97140, 15 minutes), and an OT sees the same patient at 2:00 p.m. for 30 minutes (97535). Nothing overlaps, so there’s no minute-splitting; each discipline bills its own session under its own plan.

Total for the day: 5 units, 70 minutes, two separate sessions. The PT’s 40 minutes support 3 units; 97110’s remainder after its first unit (10 minutes) beats 97140’s remainder (0), so the third unit goes to 97110.

Two things still connect the sessions without co-treatment. First, MPPR applies across disciplines: CPM §10.7 states “the MPPR applies to all therapy services furnished to a patient on the same day, regardless of whether the services are provided in one therapy discipline or multiple disciplines.” Full practice-expense payment goes to the day’s highest-PE unit, PT and OT combined, and every other unit is paid at 50 percent PE, a rate in effect since April 1, 2013. See our MPPR guide for the calculation. Second, NCCI still applies regardless of overlap: had the PT billed a re-evaluation (97164) instead, the OT’s 97535 line that day would hit the active edit above and need a modifier with supporting documentation.

Each discipline needs its own paperwork trail. BPM §220.1.2.B requires “different plans of care for each type of therapy discipline. When more than one discipline is treating a patient, each must establish a diagnosis, goals, etc. independently.” A PT may not treat under an OT’s plan, though both plans can live in one document as long as each discipline’s content (diagnosis, long-term goals, type, amount, duration, and frequency) is present and separately attributed. GP identifies the PT plan and GO the OT plan (CPM §20.B), and “always therapy” codes must carry the modifier for the plan of care they were furnished under (CPM §20.2.D). See our plan of care certification guide for what each plan must certify.

The KX threshold accrues separately by discipline too. For CY 2026, CMS’s therapy services page (last revised February 2026) sets it at “$2,480 for PT and SLP services combined, and $2,480 for OT services”: two separate thresholds, not one combined number. See our KX modifier guide for how it works.

Part A vs Part B: where the confusion comes from

Practices with SNF-trained staff often carry Part A co-treatment rules into an outpatient Part B setting, where the rules differ in kind. The CY 2026 RAI Manual (v1.20.11, effective October 1, 2026), item O0390, spells out both sides:

The payment context differs too: CMS’s Scenario 11 note states that SNF Part A therapy “services are paid as part of the bundled PPS rate and not reimbursed under the physician fee schedule as they are under Part B,” so Part A minutes feed an assessment rather than fee-schedule claim lines. O0425’s own example: an OT recorded 23, 18, and 12 minutes across three co-treatment sessions with a PT, while the PT recorded 7, 22, and 18 minutes for those same three sessions. Each discipline enters its own minutes for shared time, and under Part A those minutes don’t have to match. Under Part B, the same clock applies to both disciplines, and documented minutes cannot exceed the time the patient was actually treated.

What each discipline’s note has to show

Under BPM §220.3.E, each treatment note needs: the date of treatment; identification of each specific intervention billed, “in language that can be compared with the billing on the claim to verify correct coding,” recording every timed-code service regardless of whether it’s billed; total timed-code treatment minutes and total treatment time; and the signature and credentials of whoever furnished or supervised the service, plus a list of everyone who contributed. CMS is explicit that “the billing and the total timed code treatment minutes must be consistent.” Per-intervention time may be recorded voluntarily, but contractors “shall not require it.”

Where two plans of care exist for the same patient, BPM §220.1.2.A notes “the treatment notes continue to require timed code treatment minutes and total treatment time and need not be separated by plan”: the minute fields on a co-treatment note work the same way whether one plan or two are in play. See our documentation requirements guide for what reviewers look for in the record.

The professions also have joint guidance beyond CMS’s rules. ASHA’s “Joint Guidelines for Therapy Co-Treatment Under Medicare”, developed with AOTA and APTA (undated, accessed September 2026), is association guidance, not a payer rule: “Co-treatment is appropriate when coordination between the two disciplines will benefit the patient, not simply for scheduling convenience,” and “documentation should clearly indicate the rationale for co-treatment and state the goals that will be addressed through this method of intervention.” It also recommends limiting co-treatment to two disciplines per session and having each practitioner document which goals were addressed and what progress was made. None of that is a CMS requirement, but a reviewer asking why both disciplines were there at once is asking exactly what the guidelines say the note should already answer.

Co-treatment billing is arithmetic layered on top of arithmetic: the 8-minute rule, then a discipline split, then CQ/CO if an assistant is involved. PrismEHR serves PT, chiropractic, orthopedics, wellness, and primary care in one system, sums timed units per visit across codes as you document, and calculates the 8-minute rule automatically for Medicare patients. Organizations can define their own billing rules, including minute and unit restrictions by code and payer, enforced at documentation and reinforced again at claim creation, and units default to zero rather than prefilling from the prior visit. See our guide to multidisciplinary vs. rehab-specific EHRs, or learn more about physical therapy practices.