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CO-179 Denial Code: Waiting Period Not Met

CO-179 means the patient has not met a required waiting period. The plan requires a set amount of time to pass, after enrollment or before a specific benefit becomes available, and the service happened before that time ended.

Quick facts

Code
CO-179 (CARC 179)
Status
Active In use since June 30, 2005; last modified March 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The provider absorbs the amount from this payer's perspective, and a network contract may limit patient billing.
  • PR (Patient Responsibility): The patient is responsible because the benefit wasn't yet available. Common in dental and some supplemental plans.
Official description
Patient has not met the required waiting requirements. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-179 means

CARC 179 reads “Patient has not met the required waiting requirements.” Some plans don’t provide certain benefits until a member has been enrolled for a set time. The patient is covered, but the specific benefit wasn’t available yet on the date of service.

The usage note refers to the 835 Healthcare Policy Identification segment (loop 2110 REF). When present, it identifies the plan provision.

Example: a patient joins a dental plan with a waiting period for major services. A crown is placed three months after enrollment, before the waiting period ends. The plan denies it with CARC 179, typically under PR, leaving the patient responsible.

Common causes

  • Dental plan waiting periods for basic or major services.
  • Supplemental or limited-benefit plans with waiting periods for particular benefits.
  • Employer eligibility waiting periods where the member isn’t covered until after a set period of employment (though that more often yields a no-coverage denial).
  • Plan changes that restarted waiting periods when the patient switched carriers.
  • Registration errors in the enrollment date causing the payer to apply a waiting period incorrectly.

How to fix it

  1. Confirm the enrollment date and the plan’s waiting periods for the service.
  2. If the payer has the wrong enrollment date, ask the patient or employer to correct it with the plan, then request reprocessing.
  3. If the patient had prior continuous coverage that the plan should credit, the patient can appeal with proof, where the plan allows waiver of the waiting period.
  4. If the waiting period applies, bill the patient if the group code is PR and your agreement allows, or write off a CO amount.

How to prevent it

  • Check waiting periods during eligibility verification, especially for new enrollees.
  • Use predeterminations for major dental work in a patient’s first year of coverage.
  • Discuss costs upfront with patients whose benefits aren’t yet available and get a signed financial agreement.
  • Schedule elective services after the waiting period when clinically appropriate. See eligibility denials.

Specialty notes

Dental practices see CO-179 and PR-179 most. Medical practices encounter it mostly with supplemental or limited-benefit plans.

Remark codes that may appear with CO-179

  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Points to the plan's benefit documents where the waiting period is defined.
  • N30 (Patient ineligible for this service.): The patient is not eligible for this service yet.
  • PR-26 (Expenses incurred prior to coverage.): The service occurred before coverage started at all.
  • CO-177 (Patient has not met the required eligibility requirements.): A broader eligibility requirement was not met.
  • CO-178 (Patient has not met the required spend down requirements.): A Medicaid spend-down requirement is outstanding.

CO-179 FAQ

Which plans have waiting periods?

They're common in dental plans for major services, and in some supplemental, vision, and short-term plans. Waiting periods for pre-existing conditions are restricted in ACA-compliant major medical plans, but other waiting rules can still apply.

Will the claim be paid after the waiting period ends?

Not for services before it ended. The waiting period applies to the date of service, so only services after it ends are eligible.

Where is the waiting period defined?

In the plan's benefit documents. The usage note also points to the 835 Healthcare Policy Identification segment (loop 2110 REF), which may identify the policy.

Can a waiting period be waived?

Some plans waive or shorten waiting periods when a member had prior continuous coverage, or for certain employer groups. The patient should ask the plan and provide proof of prior coverage if requested.