This reason code is assigned when the type of bill (TOB) is equal to inpatient status code (11x, 18x, 21x, or 41x), the non-covered charges are greater than zero and equal to the total charges, and the occurrence span code (OSC) 79 or M1 is present on the claim. These OSC indicate a period of non-covered care that is not medically necessary for which Medicare will not reimburse and the provider is liable. 

Refer to the Part A Reason Code Lookup for a description associated with the Medicare Part A reason code(s). Enter a valid reason code into the box and click the submit button.

Reference

• CMS IOM Pub. 100-04 Claims Processing Manual, Chapter 3