I am doing billing for an Internal Medicine Physician/Endocrinologist who is handling medical management for Inpatient Rehab (POS 61) patients. The care is referred by the rehab specialist. The initial day is billed with CPT 99251-99255 as a consult and subsequent days are billed 99231-99233, all with POS 61. The diagnosis codes vary--25003, 4019, 2724, etc. The Inpatient rehab Facility is located within an Inpatient Hospital (POS 21). Medicare is rejecting the claims stating "Admission date is required on inpatient medical visits". I am using MPMSOFT for the billing software. The ANSI file rejection is because the admit and discharge dates are not coming up in "Segment 435" of the ANSI file. The admit and discharge dates are in the appropriate places on the hardcopy claims. I have been working with the software vendor with no luck. Can I bill these services with POS 21 instead of POS 61? I have been told that is what other physicians are doing and that is what the previous biller was doing. Please HELP!!!