CO-151
Units, frequency
- Recount in the therapy units calculator
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Insight · Therapy denials, CARC and RARC
Outpatient therapy denial codes: the CARC map, with owners
Short answer: fifteen reason codes cover most PT, OT and SLP denials. Each below with its X12 wording after the October 1, 2026 update, its remark codes, the therapy cause, the fix and the owner.
CR 14492 · effective Oct 1, 2026
CO-151 + N362 · units and frequency
CO-4 + N519 · modifier conflict
3 X12 updates a year
Edition
Oct 2026
Focus
Therapy denials
Codes
15 CARCs
Metric
3 X12 updates a year
Effective date
Oct 1, 2026
Length
6 min read
15reason codes
Most PT, OT and SLP denials; mapped to remark, cause, fix, owner [2]
Oct 12026
CR 14492, Transmittal 13791: issued May 27, implemented October 5 [1]
3per year
X12 cycles, around March 1, July 1 and November 1; re-read the map each time [1]
CO-151N362
The units and frequency denial and its remark [3]
Group code first: who pays
Group codeWhat it saysWhat you do
COContractual
ReadingYours under the contract; most of the map arrives as CO
ActionFix or appeal; route to the owner
PRPatient
ReadingDeductible, coinsurance, or non-covered with a valid ABN
ActionBill the patient; the trap is a CO-50 that should be PR
OAOther
ReadingNeither party at fault; CARC 18 duplicates
ActionDo not work these as denials
The whole designReason code: the rule. Remark: the detail. Group code: who pays. All three on one worklist line, with the owner.
Reason code, remark code, fix, owner
X12 wording as of October 2026, abridged. Plan-specific remarks vary by payer; X12 is the authority for the text, the remittance for which one was sent [2].
| CARC | X12 reason (abridged) | Remark codes seen with it | Usual therapy cause | Fix and owner |
|---|---|---|---|---|
| CO-151 | Information submitted does not support this many/frequency of services | N362 units exceed maximum; M53 invalid units | Units above timed minutes; frequency above plan or MUE | Recount from total minutes; align frequency to the plan. Coder, therapist |
| CO-4 | Procedure code inconsistent with the modifier used | N519, N823 invalid modifiers | GP, GO, GN missing or swapped; CQ or CO on an evaluation; stray 59 | Fix the modifier table per discipline. Coder |
| CO-16 | Claim lacks information or has a billing error | M51 invalid code; M53; N4 prior EOB | Deleted code; secondary without primary remit | Correct and resubmit; new code set each January. Billing |
| CO-197 | Precertification, authorization or notification absent | N54 inconsistent with pre-certified services | No auth; wrong code on the auth | Auth before the visit; auth codes match the claim. Authorization desk |
| CO-198 | Precertification, authorization or notification exceeded | N640 exceeds approved number or frequency | Visits beyond the approved count or date range | Counter per visit; timely extension. Front desk |
| CO-50 | Not deemed a medical necessity by the payer | N115 based on a Local Coverage Determination | KX without documentation; maintenance care without skilled need | Chart review against the LCD; progress toward goals. Therapist, compliance |
| CO-236 | Procedure or modifier combination not compatible under NCCI | N20 same-date service; M15 bundled | 97530 with 97140 or 97150; 97110 with 97164 same day | Check the NCCI pair; 59 or X modifier only when distinct. Coder |
| CO-97 | Benefit included in payment for another adjudicated service | M15 bundled; N390 cannot be billed separately | Evaluation and treatment same day, payer bundles | Confirm payer policy; appeal with notes. Billing |
| CO-119 | Benefit maximum for this time period reached | N130 consult plan benefit documents | Visit limit reached; threshold crossed without KX | Limits per plan; KX above the threshold. Billing, authorization desk |
| CO-B7 | Provider not certified or eligible on this date | Plan-specific text | Therapist not yet enrolled | Enrollment calendar by therapist and payer. Credentialing |
| CO-170 | Denied when billed by this type of provider | Plan-specific text | PTA or OTA billed as rendering provider | Bill under the supervising therapist, CQ or CO. Coder, credentialing |
| CO-29 | Time limit for filing has expired | Plan-specific text | Held claims; secondary claims filed late | Filing-window queue by payer. Billing |
| CO-109 | Not covered by this payer; send to the correct payer | N4 prior carrier EOB; N130 | MA billed to Original Medicare; wrong Medicaid MCO | Eligibility before the visit. Front desk |
| OA-18 | Exact duplicate claim or service | None required | Resubmitted while the original is pending | Claim status before resubmission. Billing |
| CO-252 | Attachment or documentation required to adjudicate | M127 missing record; N29 missing documentation | Records request on a KX claim or a high-unit day | Packet assembled within the window. Compliance |
Sort by owner before dollars
Owner by denial family: codes in the map per owner
In our authorization turnaround case study, auth denials fell from 3.2% of visits to 0.4% once the counter fired before the visit instead of after the remit.
Coder or therapistunits, modifiers, necessity
6 codes40% of the map
Authorization and front deskauth, limits, eligibility
5 codes33%
Billingfiling, duplicates, bundling
4 codes27%
Credentialing and complianceenrollment, records
3 codes20%
Clinical and codingFront endBillingCredentialing, compliance
Where each gets prevented
CO-50 and CO-252
Necessity, records
CO-197, CO-198, CO-119
Auth, limits
- Visit limits and auth vendors by state: therapy payer matrix
Takeaway
A reason code report that lands on one team is a worklist; one that lands on everyone is a meeting. Fifteen codes, four owners, one line each.
Keep the map current
Calendar the three X12 update cyclesContractors use the X12 effective date when it differs from the CR.
Check the January code set and BB, BC modifiersElse every telehealth line risks CO-4.
Add the owner column to the denial reportGroup code, CARC, RARC, owner.
Run 90 days of remits through the mapThe free denial audit does it; our PT and OT billing teams work denials in this shape.
Frequently asked questions
What does CO-151 mean on a physical therapy claim?
"Payment adjusted because the payer deems the information submitted does not support this many/frequency of services." Units exceed timed minutes, or frequency exceeds the plan or a payer limit; N362 often rides with it.
Which remark codes go with CO-4 on therapy claims?
N519, invalid combination of HCPCS modifiers, and N823, invalid procedure modifiers: GP, GO or GN missing or swapped, CQ or CO on an evaluation, or 59 where not valid.
How often do CARC and RARC codes change?
Three times a year, around March 1, July 1 and November 1. CR 14492 loaded the July 1, 2026 publication, effective October 1, 2026.
What is the difference between CO and PR on a denial?
Who is responsible. CO: the provider absorbs or appeals. PR: billable to the patient, deductible, coinsurance or non-covered with a valid Advance Beneficiary Notice. OA: other adjustments such as duplicates.
- CMS Transmittal 13791, CR 14492: CARC, RARC, MREP and PC Print update (May 27, 2026; effective October 1, 2026)
- X12, Claim Adjustment Reason Codes (current list)
- X12, Remittance Advice Remark Codes (current list)
- Medicare Claims Processing Manual, Chapter 5, section 20.2, service units
- CMS, Therapy Services: KX modifier thresholds, CQ/CO modifiers
Checked October 25, 2026. Rules change; confirm against the source.
Want 90 days of therapy denials mapped this way?
Send the remittance file; we return reason codes grouped by owner, dollars behind each, and the three fixes that would have prevented the most.