How to Bill Medicare for Occupational Therapy: CPT Codes, Modifiers & Documentation

Your therapists help a stroke patient button a shirt again, or teach a patient with arthritis a safer way to cook. That work is skilled, and Medicare pays for it. But Medicare only pays when the claim tells the right story: the right CPT codes, the right units, the right modifiers, and notes that prove the care was needed.

That is where many outpatient OT practices lose money. Occupational therapy billing has rules that general medical billing does not, such as the 8-minute rule, the KX threshold, and the 15% cut when an assistant treats the patient. Miss one rule and the claim is denied, underpaid, or pulled into review months later.

This guide walks through how Medicare occupational therapy billing really works in 2026. It covers the OT CPT codes you bill most, the occupational therapy modifiers Medicare expects, the documentation auditors look for, and where revenue quietly leaks. It also shows how a dedicated billing team protects that revenue so your therapists can stay focused on patients.

How do you bill Medicare for occupational therapy? Bill outpatient OT under Medicare Part B on a CMS-1500 or 837P claim. Use an OT evaluation code (97165, 97166 or 97167), then timed treatment codes such as 97530 or 97535, counted in 15-minute units under the 8-minute rule. Add the GO modifier to every line. Add KX once yearly OT charges pass $2,480 (2026) and care is still medically necessary, and CO when an OT assistant provides more than 10% of a service. Keep a signed plan of care, recertified at least every 90 days, and a progress report at least every 10 visits.

How Medicare Pays for Outpatient Occupational Therapy

Outpatient OT falls under Medicare Part B. After the patient meets the yearly Part B deductible, Medicare pays 80% of the approved amount and the patient owes the other 20%. Payment comes from the Medicare Physician Fee Schedule, so each OT CPT code has a set value.

Each state has a Medicare Administrative Contractor (MAC), the company that processes claims for Medicare. In Florida, that is First Coast Service Options. The MAC applies national rules, plus its own local edits and review focus. A claim that passes in one state can still stall in another.

Three things decide whether a Medicare OT claim gets paid in full:

1. The codes and units match the minutes in the daily note.

2. The modifiers tell Medicare who gave the care and where the patient is in their yearly therapy spend.

3. The documentation proves the care was skilled and medically necessary, under a plan of care a physician signed.

The rest of this guide breaks down each one.

Occupational Therapy CPT Codes Medicare Practices Bill Most

OT CPT codes fall into two groups. Untimed codes are billed once per session, no matter how long it lasts. Timed codes are billed in 15-minute units, so the minutes in the note drive the payment.

The evaluation code depends on complexity, not on how long the visit took. Complexity is set by the patient's history, the number of performance deficits, and how much clinical decision-making the case needs. Picking 97167 when the note supports only 97166 is a classic audit finding. Picking 97165 when the case was complex leaves money on the table.

OT codes also run into National Correct Coding Initiative (NCCI) edits, which block some code pairs on the same day. A common one: 97530 billed on the same day as an evaluation. It can be paid only when the activity is separate and distinct, shown with modifier 59 and a note that supports it. Many common medical coding errors in therapy practices come from edits like this one.

The 8-Minute Rule: How OT Units Are Counted

Medicare counts timed OT units with the 8-minute rule. Add up all timed minutes in the session, divide by 15, and a leftover of 8 minutes or more earns one more unit.

The tricky part is splitting units across codes. Say a therapist gives 33 minutes of 97530 and 7 minutes of 97535. Total timed minutes are 40, so the visit earns 3 units. Two go to 97530, and the third also goes to 97530 because it has the most minutes left over. Billing 97535 for that third unit would not match the note.

Untimed minutes, such as the evaluation, never count toward the total. Rest breaks and set-up time do not count either. When units and minutes disagree, Medicare can deny the extra unit, or take money back in a later audit.

Occupational Therapy Modifiers Medicare Expects

Occupational therapy modifiers carry information the codes cannot. Missing or wrong modifiers are one of the fastest ways to get an OT claim denied.

GO is the one practices most often forget on a single line. Without it, the line can be rejected even when everything else is correct. If the patient also sees physical therapy, those lines carry GP instead, and the two disciplines must stay on separate plans of care.

The KX threshold in 2026

Medicare no longer has a hard cap on therapy. Instead, CMS sets a yearly KX threshold. For 2026 it is $2,480 for OT, and a separate $2,480 for PT and speech therapy combined. Once a patient's allowed OT charges for the year pass that amount, every OT line must carry KX. Lines without it are denied.

KX is a promise, not a pass. By adding it, the practice states the care is still medically necessary and the notes prove it. Above $3,000, claims can be picked for targeted medical review. The threshold counts charges from every OT provider the patient saw that year, not just yours. A patient who used most of their amount at another clinic in spring can cross the line on your second visit.

The CO modifier and the 15% cut

When an occupational therapy assistant (OTA) gives more than 10% of a service, Medicare pays 85% of the normal rate. The line needs the CO modifier. Getting this wrong cuts both ways. Leave CO off when it applies, and the claim overstates who gave the care, a compliance risk. Add it when the OTA's time was under the 10% de minimis limit, and you give away 15% you earned.

CMS also lets the supervising therapist meet direct supervision through a real-time audio and video link, which is now a permanent rule. That gives practices more flexibility in how they staff OTAs.

Multiple procedure payment reduction

When a patient gets more than one therapy unit on the same day, Medicare lowers the practice expense part of every unit after the first by 50%. This is the multiple procedure payment reduction (MPPR). It is expected, not an error. But it means your expected payment per visit is lower than adding up the full fee schedule. Practices that do not model it often think a payer underpaid them, or miss a real underpayment hiding behind it.

Documentation Medicare Needs to Pay OT Claims

Codes and modifiers get a claim through the door. Documentation decides whether the money stays paid. Medicare can review OT claims months after payment and take back every dollar the notes do not support.

These are the records an auditor checks first:

The word that matters most is skilled. Medicare pays for care that needs a therapist's judgment, not for repeat exercises a patient could do alone at home. A note that says "patient tolerated treatment well" proves nothing. A note that says the therapist graded a dressing task, cued compensatory strategies, and measured a change in independence proves skilled care.

An unsigned plan of care is one of the most expensive gaps in OT billing. Without a timely certification, every visit under that plan can be denied, even when the treatment was excellent. Recertification dates slip easily when a caseload is full, so they need a tracking system, not memory.

Telehealth for OT in 2026

Occupational therapists and OTAs can bill Medicare for telehealth through December 31, 2027. Coverage is code-specific, and most services need real-time audio and video. The visit still needs the same documentation, plus the place of service and the 95 modifier where the payer requires it.

Where Occupational Therapy Practices Lose Medicare Revenue

Most lost OT revenue is not one big denial. There are many small leaks that repeat every week. These are the patterns we see most in OT medical billing:

• Missing GO on one line. One bare line on a multi-line claim can reject or delay payment.

• KX added too late. The front desk does not know the patient used therapy dollars at another clinic, so claims above $2,480 go out without KX and come back denied.

• Units that do not match minutes. The note shows 37 timed minutes, but three units were billed.

• Lapsed certifications. The 90-day receipt passes unsigned, and every visit after it is at risk.

• CO errors. Assistant time is not tracked by line, so CO is either missed or added when it was not needed.

• Evaluation complexity that does not match the note. This is a common audit target and a common source of underbilling.

• Denials that are never worked. Small OT claims get written off because no one has time to appeal them.

Each of these traces back to reasons Medicare claims are denied that are preventable with the right checks before the claim goes out.

Should You Handle OT Billing In House or Outsource It?

In-house billing can work for a small OT practice with an experienced biller who knows therapy rules well. It gets hard when that person also answers phones, checks eligibility, and posts payments. Therapy rules change every year, and a missed update to the KX amount or a new NCCI edit hits every claim at once.

Outsourcing makes sense when you see signs like these: denials are rising, KX denials keep coming back, claims sit for more than 30 days, or your therapists spend evenings fixing billing questions. A billing partner that focuses on therapy tracks the rules, the thresholds, and the deadlines for you, and works every denial to the end.

How Avorcms Services Helps With Medicare Occupational Therapy Billing

Avorcms Services provides occupational therapy billing services built around how outpatient OT practices actually work. We do not hand your team a checklist and wish you luck. We take the billing work off your desk and stay accountable for the result.

Here is what that looks like day to day:

• Eligibility and therapy history checks before the first visit, so we know how much of the patient's yearly threshold is already used and when KX must start.

• Code and unit review on every claim, matching each unit to the minutes in the note and flagging NCCI edits before submission.

• Modifier accuracy on every line: GO, KX, CO, 59 and GA applied only where the record supports them.

• Plan of care tracking, with alerts before certifications and recertifications fall due.

• Therapy claim denial management that finds the root cause, corrects it, and appeals with the right records attached.

• Clear monthly reporting on collections, denials, and A/R, with a dedicated account manager who knows your practice.

We work with outpatient OT, PT and speech practices as part of our billing for therapy and rehabilitation practices. Based in St. Petersburg, we provide occupational therapy billing services in Florida and support providers across the United States.

Find Out What Your OT Claims Are Really Worth

If your OT claims are being denied, paid late, or paid less than you expect, the problem is usually hiding in a few repeat errors. Our team will review your recent Medicare OT claims, check codes, units, modifiers and certifications, and show you where revenue is slipping.

Start with a free medical billing audit, call (727) 662 8558, or email [email protected]. We respond within 24 hours.

Frequently Asked Questions

1. What modifier does Medicare require for occupational therapy? Medicare requires the GO modifier on every occupational therapy line. It shows the service was given under an OT plan of care. Physical therapy uses GP and speech therapy uses GN.

2. What is the KX modifier threshold for occupational therapy in 2026? The 2026 KX threshold is $2,480 for OT services. Once a patient's allowed OT charges for the year pass that amount, each OT line needs KX to show the care is still medically necessary.

3. Is there still a Medicare cap on occupational therapy? No. The hard cap ended in 2018. Medicare now uses the KX threshold, plus targeted medical review for some claims above $3,000.

4. What are the OT evaluation CPT codes? OT evaluations use 97165 for low complexity, 97166 for moderate complexity, and 97167 for high complexity. Re-evaluations use 97168. All four are untimed and billed once per visit.

5. How does the 8-minute rule work for OT? Add all timed minutes in the session and divide by 15. A leftover of 8 minutes or more adds one unit, so 8 to 22 minutes is one unit and 23 to 37 minutes is two.

6. When do you use the CO modifier? Use CO when an occupational therapy assistant provides more than 10% of a service. Medicare then pays that service at 85% of the normal rate.

7. How often does an OT plan of care need recertification? A physician or nonphysician practitioner must recertify the plan at least every 90 days, or sooner if the plan changes. The first certification should be signed within 30 days of the first treatment.

8. Can occupational therapists bill Medicare for telehealth in 2026? Yes. OTs and OTAs can bill eligible telehealth services through December 31, 2027. Most visits need real-time audio and video, and coverage is code-specific.

9. Why are Medicare OT claims denied most often? The most common causes are a missing GO or KX modifier, units that do not match documented minutes, a lapsed plan of care certification, and NCCI edits billed without support.

10. Does Avorcms Services offer occupational therapy billing services in Florida? Yes. Avorcms Services is based in St. Petersburg and handles Medicare and commercial OT billing for Florida practices and providers across the United States. Call (727) 662 8558 or email [email protected].

Disclaimer: This blog is for informational and educational purposes only and does not constitute legal, compliance, or financial advice. Medicare and payer rules change often. Always confirm current requirements with CMS and your Medicare Administrative Contractor.