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CO-P13 Denial Code: Workers' Comp Regulation or Policy

CO-P13 means the workers' compensation payer reduced or denied payment based on the jurisdiction's workers' comp regulations or payment policies, and no more specific code applied. The cited regulation and remark codes explain the actual reason.

Quick facts

Code
CO-P13 (CARC P13)
Status
Active In use since November 1, 2013; last modified July 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The adjustment follows workers' comp rules, and the injured worker generally can't be billed for it.
Official description
Payment reduced or denied based on workers' compensation jurisdictional regulations or payment policies, use only if no other code is applicable. Usage: If adjustment is at the Claim Level, the payer must send and the provider should refer to the 835 Insurance Policy Number Segment (Loop 2100 Other Claim Related Information REF qualifier 'IG') if the jurisdictional regulation applies. If adjustment is at the Line Level, the payer must send and the provider should refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment information REF) if the regulations apply. To be used for Workers' Compensation only.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-P13 means

CARC P13 says payment reduced or denied based on workers’ compensation jurisdictional regulations or payment policies, use only if no other code is applicable. X12 limits it to workers’ compensation. It replaced deactivated CARC W2.

States regulate workers’ comp medical care in detail: which services are payable, how often, with what documentation, and under which billing rules. When a payer reduces or denies a bill under one of those rules and no more specific CARC fits, it uses P13. That makes P13 a catch-all, and the regulation reference is where the real explanation lives.

The usage note says the payer must send the regulation: at claim level in the 835 insurance policy number segment (loop 2100 REF qualifier IG), and at line level in the healthcare policy identification segment (loop 2110 REF), when the regulations apply.

Common causes

  • Frequency limits set by state rules (N640).
  • Once-per-injury services billed more than once (N636).
  • Non-payable administrative charges, such as certain report or form fees.
  • State billing rules for modifiers, units, or claim forms.
  • Services outside the accepted body parts or conditions, depending on how the state handles it.

How to fix it

  1. Read the remark codes and the cited regulation.
  2. Look up the rule in the state’s workers’ comp regulations or payment policies.
  3. If you billed incorrectly, correct the bill and resubmit under the state’s rules.
  4. If the rule was misapplied, request reconsideration with documentation, then use the state’s dispute process within its deadlines.
  5. Don’t bill the injured worker for amounts adjusted under state rules unless state law allows it.

How to prevent it

  • Know the workers’ comp billing rules for each state you serve, including frequency limits and required reports.
  • Get authorization for treatment where the state or carrier requires it.
  • Train billers on state-specific modifiers and forms.
  • Track P13 adjustments by state and rule. An ERA Analyzer can reveal patterns that point to a billing rule you’re missing.

Specialty notes

PT and chiropractic practices often hit workers’ comp visit limits and treatment frequency rules. Behavioral health providers treating injured workers should check state rules for psychological evaluations and treatment authorization.

Remark codes that may appear with CO-P13

  • N640 (Exceeds number/frequency approved/allowed within time period.): Exceeds the number or frequency approved or allowed within a time period.
  • N636 (Adjusted because this is reimbursable only once per injury.): Reimbursable only once per injury.
  • N621 (Charges for Jurisdiction required forms, reports, or chart notes are not payable.): Charges for jurisdiction-required forms, reports, or chart notes aren't payable.
  • CO-W2Deactivated (Payment reduced or denied based on workers' compensation jurisdictional regulations or payment policies, use only if no other code is applicable.): The deactivated code that CARC P13 replaced.
  • CO-P12 (Workers' compensation jurisdictional fee schedule adjustment.): A workers' comp fee schedule reduction, which should be used instead when pricing is the reason.
  • CO-P15 (Workers' Compensation Medical Treatment Guideline Adjustment.): A workers' comp medical treatment guideline adjustment.
  • CO-P1 (State-mandated Requirement for Property and Casualty, see Claim Payment Remarks Code for specific explanation.): A state-mandated P&C requirement explained by a remark code.

CO-P13 FAQ

Why is CO-P13 so vague?

X12 designed it as a fallback: 'use only if no other code is applicable.' The specific reason comes from the jurisdictional regulation the payer cites and any remark codes.

Where do I find the regulation?

At claim level, in the 835 insurance policy number segment (loop 2100 REF, qualifier IG). At line level, in the healthcare policy identification segment (loop 2110 REF), when the regulations apply.

Can I dispute CO-P13?

Yes. Ask the payer for the specific rule if it isn't clear, then request reconsideration and use the state's dispute process if you believe the rule was misapplied.

Does CO-P13 apply outside workers' comp?

No. X12 limits it to workers' compensation claims.