RARC N321: Missing or Invalid Last Admission Period
The claim is missing or has incorrect admission dates — review and correct the last admission period on the claim form, particularly for inpatient or facility-based services.
What Does RARC N321 Mean?
RARC N321 fires when the payer detects that the last admission period on the claim is either missing entirely, contains incomplete dates, or has dates that do not pass validation. The admission period is essential for inpatient and facility-based claims because the payer uses it to determine coverage, calculate per-diem rates, verify benefit days remaining, and coordinate with other claims for the same patient.
This code commonly appears on UB-04 institutional claims where the statement covers period (Form Locator 6) or the admission date (Form Locator 12) is blank, contains an impossible date, or conflicts with other dates on the claim. It can also surface when a claim references a prior admission period that the payer cannot verify — for example, a readmission claim that cites the original admission dates incorrectly.
N321 is a data integrity issue. The payer is not making a coverage determination — it simply cannot proceed with adjudication until the admission period is correctly reported. Once corrected, the claim typically processes without further issues related to this code.
What to Do
Review the claim form for the admission date, discharge date, and statement covers period. Confirm that the admission date is present and formatted correctly, that it falls before or on the discharge date, and that the statement covers period aligns with the actual dates of the inpatient stay. Cross-reference these dates against the patient's medical record to ensure accuracy.
If the claim involves a readmission and references a prior admission period, verify that the prior dates are also correct. Correct any missing or invalid dates in your billing system and resubmit the claim. For electronic claims, check that the date fields in the 837I transaction are properly formatted (CCYYMMDD) and that no required date segments have been omitted.
Common Scenarios
- An inpatient claim is submitted with the admission date field left blank because it was not captured in the billing system during registration
- The admission date on the claim is entered as a future date due to a data entry error, failing the payer's date validation
- A claim for a readmission references the original admission period incorrectly, causing the payer to reject the claim for invalid dates
- The statement covers period on a UB-04 claim shows dates that do not match the admission and discharge dates, triggering N321
Commonly Paired With
No common pairings documented yet.