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N305 Remark Code: Injury or Accident Date Invalid

N305 means the date of the injury or accident was missing, incomplete, or invalid. When a claim indicates an accident or injury, the payer needs a valid date to decide coverage and whether another payer, such as auto or workers' compensation, is responsible.

Code: N305 (RARC N305)
Status: Active In use since December 2, 2004; last modified November 1, 2016.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): The provider must supply a valid accident date. The adjustment isn't billable to the patient while the data is correctable.
Official description: Missing/incomplete/invalid injury/accident date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What N305 means

Accidents and injuries change who pays. Health plans may coordinate with auto insurers, liability carriers, or workers’ compensation, and some benefits depend on when the injury happened. For that reason, whenever a claim says a condition resulted from an accident, the payer expects the accident date. N305 tells you the date was missing or unusable.

The X12 list shows this remark was last modified in 2016. It is typically paired with CARC 16. Once the date is supplied, the payer may decide another carrier is primary, which would produce a different reason code.

Common causes

Box 10 indicates an accident, but no date was entered in box 14 or 15 or in the electronic accident date.
The date given is later than the date of service, or in the future.
The accident date was reported with the wrong qualifier, or in a box the payer does not use for it.
On facility claims, an accident occurrence code has no date or an implausible one.
Registration captured the accident in free text, and billing never pulled the date into the claim.

How to fix it

Review intake notes and the clinical record for the date the injury occurred.
Confirm which accident type applies (employment, auto, other).
Enter the date where the payer instructs (on the CMS-1500, box 14 or box 15 with the correct qualifier) or in the 837 accident date, and check box 10a-c. On UB-04s, correct the accident occurrence code and date.
If another payer is responsible, bill it first; our COB guide explains the order of benefits.
Resubmit the corrected claim with frequency code 7.

How to prevent it

Ask about accidents and injury dates at registration, in structured fields. Build a claim edit that blocks any claim where an accident indicator is “yes” but no accident date is present.

Codes that may appear with N305

CO-16 (Claim/service lacks information or has submission/billing error(s).): Missing or invalid information; N305 points to the injury or accident date.
OA-19 (This is a work-related injury/illness and thus the liability of the Worker's Compensation Carrier.): The payer determined the injury is work-related and belongs to workers' compensation.
CO-20 (This injury/illness is covered by the liability carrier.): The injury is covered by a liability carrier.
CO-21 (This injury/illness is the liability of the no-fault carrier.): The injury is the responsibility of the no-fault carrier.

N622 (Not covered based on the date of injury/accident.): The service isn't covered based on the date of injury or accident.
N744 (Adjusted because the services may be related to an auto/other accident.): Adjusted because the services may be related to an auto or other accident.
N299 (Missing/incomplete/invalid occurrence date(s).): Another occurrence date is missing or invalid.

N305 FAQ

Where does the accident date go on a CMS-1500?

Under the NUCC instructions, box 14 reports the date of current illness, injury, or pregnancy, and box 15 has an Accident qualifier (439) for reporting an accident date. Box 10a-c indicates whether the condition relates to employment, an auto accident, or another accident. Electronic claims carry an accident date when an accident is indicated. Payers, including Medicare, can give their own instructions for these boxes.

What about institutional claims?

UB-04 claims report accident-related occurrence codes with their dates in form locators 31 to 34.

If I mark 'no' for all accident questions, do I need a date?

Usually not. N305 typically appears when the claim signals an accident or injury, or when the payer's records suggest one, but no valid date is provided.

Important: read before using this information

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