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N148 Remark Code: Missing or Invalid LMP Date

N148 means the date of the patient's last menstrual period (LMP) was missing, incomplete, or invalid on the claim. Payers use the LMP for pregnancy-related services, so the claim could not be processed without a valid date.

Quick facts

Code
N148 (RARC N148)
Status
Active In use since October 31, 2002.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): A correctable data error. Add or fix the LMP date and resubmit rather than billing the patient.
Official description
Missing/incomplete/invalid date of last menstrual period.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N148 means

For pregnancy care, payers use the last menstrual period to anchor the timeline: estimating gestational age, checking that services fit the stage of pregnancy, and tracking global obstetric periods. N148 tells you the claim lacked a usable LMP date.

It is almost always paired with CARC 16.

Where the LMP goes

  • CMS-1500: box 14, with the qualifier 484 identifying the date as the last menstrual period, per the NUCC instructions. Medicare’s CMS-1500 instructions say not to enter a qualifier in item 14, so follow the payer’s own rules.
  • 837P: the claim-level date information, reported with the last menstrual period qualifier. Your clearinghouse maps box 14 data to this field.

Common causes

  • Box 14 was left blank on an obstetric claim.
  • A date was entered but with the onset qualifier (431) instead of LMP.
  • The date was keyed with a typo, producing a future or impossible date.
  • The LMP was captured in the clinical record but not transferred to the billing system.
  • A later visit used a different LMP than the one on earlier claims, causing an inconsistency.

How to fix it

  1. Pull the LMP from the prenatal record.
  2. Enter it correctly with the LMP qualifier.
  3. Send a corrected claim with resubmission code 7 in box 22 and the original claim number, or a new claim if the original was rejected before processing.
  4. Check other open claims for the same pregnancy and correct them too.

How to prevent it

Make the LMP a required field for obstetric encounters in your practice management system, and pull it automatically from the prenatal record. A pre-submission rule that requires box 14 on pregnancy diagnosis claims catches the gap before it reaches the payer.

Codes that may appear with N148

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim lacks information needed for adjudication; N148 names the LMP date.
  • CO-A1 (Claim/Service denied.): A general claim denial explained by the missing date.
  • N80 (Missing/incomplete/invalid prenatal screening information.): Missing or invalid prenatal screening information.
  • CO-7 (The procedure/revenue code is inconsistent with the patient's gender.): The procedure is inconsistent with the patient's gender, another edit on obstetric claims.
  • CO-14 (The date of birth follows the date of service.): The date of birth follows the date of service, a different date-logic error.

N148 FAQ

Where does the LMP go on a paper claim?

On the CMS-1500, box 14 holds the date of current illness, injury, or pregnancy. Enter the LMP date with the qualifier for last menstrual period (484).

What makes an LMP date invalid?

A date after the date of service, an impossible date, a date inconsistent with the pregnancy timeline, or a missing qualifier.

Do all pregnancy claims need an LMP?

Requirements vary by payer and service. Many payers expect it on obstetric and pregnancy-related claims; check the payer's billing guide.