When Do You Add Modifier KX to Therapy Claims?
Add modifier KX to a Medicare outpatient therapy line once the patient's therapy for the calendar year passes the KX threshold and the record supports the care. For calendar year 2026 the CMS amounts are $2,480 for physical therapy and speech-language pathology combined and $2,480 for occupational therapy. Claims above the threshold without KX are denied.
Written by Salman Saeed, CEO and Co-Founder · Reviewed by a Certified Medical Coder · 
In short: KX is an attestation that the care is reasonable, needs a therapist's skills and is backed by the record. The threshold amounts change every year, so the claim needs the current figure, GP, GO or GN still goes on the line, and the provider is liable if the denial is for missing KX.
What Is the KX Threshold for 2026, and What Counts Toward It?
CMS Transmittal 13437, issued October 30, 2025, sets the KX modifier thresholds for calendar year 2026 at $2,480 for physical therapy and speech-language pathology services combined and $2,480 for occupational therapy services. The KX code page covers the modifier itself, and this post is the working routine for therapy claims.
| 2026 amount | Figure | What it does |
|---|---|---|
| KX threshold, PT and SLP combined | $2,480 | Claims above it without KX are denied |
| KX threshold, OT | $2,480 | Counted separately from PT and SLP |
| Medical record (MR) threshold, each group | $3,000 | Targeted medical review. Stays at $3,000 until CY 2028, then follows the Medicare Economic Index |
Chapter 5, section 10.3 of the Medicare Claims Processing Manual says contractors apply the thresholds to the fee schedule amount, or the amount charged if that is smaller, for each beneficiary. Medicare applies them in the order claims are received, and the Common Working File tracks the total. Your own running total can lag behind that figure, so confirm the accrued amount with your MAC before the visit that may cross it.
How Do You Handle the Visit That Crosses the Threshold?
Add KX to the therapy lines of the visit that carries the patient over the threshold. Later visits that year are over it too, so the same rule applies. Chapter 5, section 10.3.3 says the GN, GO or GP therapy modifier still goes on the line in addition to KX, in any order. The example below uses made-up allowed amounts.
A patient has $2,410 of PT allowed amounts this year. Today's visit has therapeutic exercise for 2 units ($62 allowed) and manual therapy for 1 unit ($29 allowed). The visit brings the year to $2,501.
On a professional claim to the A/B MAC, chapter 5 says KX is only appropriate on a service that reasonably may exceed the threshold, and calls it abusive to add KX when nothing suggests it will be reached, such as low-cost services early in an episode. On an institutional claim, once at least one line passes the threshold, KX goes on every line for the same group, PT and SLP together or OT alone.
A physical therapist assistant can add one more modifier. The CMS Therapy Services page says a portion of a service furnished by the assistant beyond the 10 percent de minimis standard is reported with CQ alongside GP. The CMS-1500 holds four modifiers per line, and chapter 5 says to put 99 in box 24D and the others in box 19 when there are more.
What Does the Record Have to Show?
By adding KX, the provider attests that the services are reasonable and necessary and need a therapist's skills, are justified by documentation in the record, and qualify for the automatic process exception. If the attestation is wrong, chapter 5 says the provider is subject to sanctions. The documentation list comes from the Medicare Benefit Policy Manual, chapter 15, section 220.3.
- The initial evaluation and any re-evaluation, with the plan of care and the physician or nonphysician practitioner's certification
- Progress reports at least once every 10 treatment days, written by the clinician
- A treatment note for every treatment day
- Evidence that the clinician's skills were needed, such as the changes made to treatment and why
- An optional justification statement when care is more extensive than typical for the condition
The manual says contractors consider the whole record, so a missing item does not undo medical necessity if the rest of the record shows it. It also says a justification statement is not required when the record already explains the treatment. Read the LCD for your region as well, because chapter 5 says KX shall not be added to a service that a local coverage determination says is not medically necessary. The LCD and NCD rules page explains where to find them.
What Happens When KX Is Missing, and How Do You Recover?
A claim for services above the threshold without KX is denied. CMS does not name a reason code for that denial, so match the remittance to the line. The route back depends on why KX was missing.
| Situation | What to do | Source |
|---|---|---|
| KX was left off, and the record supports the care | Ask the MAC to reopen or adjust the claim. Chapter 5 says contractors may do so when appending KX would have been right and it is brought to their attention | Claims Processing Manual ch. 5, 10.3.3 |
| KX was left off, and the record does not support the care | Do not add KX after the fact. The services stay denied | Same section |
| Services past the threshold that do not qualify | Bill for a denial using condition code 21 | Same section |
| The claim was denied for missing KX and no valid ABN was given | The therapist or therapy provider is financially liable | Benefit Policy Manual ch. 15, 220.2 |
| KX added, then denied as not medically necessary | Appeal with the evaluation, plan of care, progress reports and treatment notes | Benefit Policy Manual ch. 15, 220.3 |
These thresholds belong to Medicare Part B. Medicare Advantage and commercial plans may use their own visit limits and modifier rules, so read the plan's therapy policy before copying this routine. The broader claim picture is in the physical therapy billing guide, and the Medicare payer page covers the program overall.
How Nucleus Align Handles It
Our medical coding team includes AAPC and AHIMA certified coders, and we work denials within 48 hours. We watch each patient's running therapy total so KX goes on the right visit, support that fits physical therapy billing. Book a call to review your therapy claims, or read more on the blog.
- Transmittal 13437, 2026 Annual Update of Per-Beneficiary Threshold Amounts (CR 14252) · CMS
- Therapy Services · CMS
- Medicare Claims Processing Manual, chapter 5, section 10 · CMS
- Medicare Benefit Policy Manual, chapter 15, sections 220.2 and 220.3 · CMS
We check every rule, code and deadline against the official source. See our editorial policy.
Common Questions
Straight answers from the team that does the work.
Ask a billing lead directly. A 20-minute call, Monday to Friday, 9am to 5pm Eastern.
01When do you add modifier KX to therapy claims?
Add KX to Medicare outpatient therapy lines once the patient's incurred therapy expenses pass the KX threshold for the year and the record supports the care. For 2026 that is $2,480 for PT and speech-language pathology combined and $2,480 for OT. Claims above the threshold without KX are denied.
02Does KX replace the GP, GO or GN modifier?
No. Chapter 5, section 10.3.3 of the Medicare Claims Processing Manual says the GN, GO or GP therapy modifier continues to be required in addition to KX, and the modifiers may be reported in any order. KX confirms medical necessity above the threshold, and the GP, GO or GN modifier shows which plan of care.
03Can I add KX to every therapy line to be safe?
No. On professional claims, chapter 5 says KX belongs on services that reasonably may exceed the threshold and calls using it with no sign the threshold will be reached abusive. Adding KX is an attestation, and an inaccurate one can bring sanctions.
04What happens if I forget KX above the threshold?
The services are denied. Chapter 5 says contractors may reopen or adjust the claim if appending KX would have been appropriate and it is brought to their attention. If you gave no valid ABN, the benefit policy manual makes the therapist or therapy provider financially liable for the denied services.
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