Reason Code 31605
Claim contains occurrence span code 74, 76, 77, 79 or M1, and a line item date of service has been billed that is within the span from and thru dates with covered charges greater than zero.
A line item date of service, which is equal to the span code "from" or "through" dates are acceptable for occurrence span code 74 only. Correct and resubmit.
CMS Internet Only Manual (IOM), Publication, chapter 1 (PDF).