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N640 Remark Code: Frequency Limit Exceeded

N640 means the service went over the number of times the payer approved or allows within a time period, such as visits per year or units per authorization. The lines beyond the limit are reduced or denied.

Quick facts

Code
N640 (RARC N640)
Status
Active In use since July 15, 2013.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The excess services are the provider's responsibility, typically because an approval or policy limit was not followed. The patient generally cannot be billed unless they agreed in advance where the payer allows that.
  • PR (Patient Responsibility): The plan's benefit limit was reached and the member may be responsible for services beyond it, subject to plan terms and any required advance notice.
Official description
Exceeds number/frequency approved/allowed within time period.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N640 means

Many services come with a counter. A therapy authorization may approve a fixed number of visits, a plan may cover a set number of sessions per benefit year, and a policy may allow a test only once in a defined period. N640 means this claim pushed the count past that ceiling, so the payer cut the lines that went over.

The remark covers two different sources of the limit:

  • Approved — a number granted in a prior authorization or referral.
  • Allowed — a limit written into the plan’s benefits or the payer’s medical policy.

The accompanying reason code usually points to which one. CARC 198 suggests an authorization count, CARC 119 a benefit maximum, and CARC 151 a frequency the payer does not consider supported.

Common causes

  • Visits continued after the authorized count was used up, without an extension.
  • The authorization expired, so services after the end date fell outside the approval.
  • Another provider billed the same service for the patient, consuming part of the shared annual limit.
  • Units were reported incorrectly, making one visit look like several (see MUE denials and units of service).

How to fix it

  1. Identify the limit from the authorization letter, the plan’s benefits, or the payer’s policy, and count the services it has already paid.
  2. Correct unit errors and send a corrected claim with resubmission code 7 in box 22 if the count was inflated by a billing mistake.
  3. Request an extension or review if the payer allows additional services on medical necessity, with progress notes supporting continued care.
  4. Appeal when the payer’s count is wrong, such as services attributed to the wrong member or an authorization number that was not linked.

How to prevent it

Track remaining visits against each authorization and each benefit limit, and ask for an extension before the last approved visit. Verifying remaining benefits at intake helps too. See authorization and referral denials for a workflow.

Codes that may appear with N640

  • PR-119 (Benefit maximum for this time period or occurrence has been reached.): Benefit maximum for the time period has been reached.
  • CO-151 (Payment adjusted because the payer deems the information submitted does not support this many/frequency of services.): The payer deems the information submitted does not support this many services or this frequency.
  • CO-198 (Precertification/notification/authorization/pre-treatment exceeded.): The number of services exceeded what the authorization approved.
  • N435 (Exceeds number/frequency approved /allowed within time period without support documentation.): The same frequency problem, specifically where no supporting documentation was sent.
  • N636 (Adjusted because this is reimbursable only once per injury.): A limit counted per injury rather than per time period.
  • N666 (Only one evaluation and management code at this service level is covered during the course of care.): A limit on repeating the same level of evaluation and management service during a course of care.

N640 FAQ

Is N640 about an authorization or a plan limit?

It can be either. The wording covers both an approved number (from an authorization) and an allowed number (from the plan or policy). The paired CARC and the payer's records tell you which one applies.

Can more visits be approved after the fact?

Some payers accept a request to extend an authorization or review medical necessity for additional visits, but many do not allow retroactive approval. Check the payer's policy.

Can I bill the patient for services over the limit?

Only if the group code is PR or the plan and any applicable notice rules allow it. Under CO, the amount is typically the provider's write-off.