On October 29, 2010, CMS issued a transmittal offering guidance to subsection (d) hospitals (and entities wholly owned or wholly operated by subsection (d) hospitals) on how to bill “unrelated” outpatient nondiagnostic services furnished to inpatients during the three calendar days preceding an inpatient admission—the so-called 3-day DRG payment window. The transmittal states that hospitals may bill for such nondiagnostic services as separate services if the hospital attests that the services are unrelated to the admission. Hospitals may make such an attestation using Condition Code 51 (“Attestation of Unrelated Outpatient Non-diagnostic Services”) for each unrelated service appearing on an outpatient claim. The transmittal defines “unrelated” services as those that are “clinically distinct or independent from the reason for the beneficiary's admission.” CMS remained silent, however, on the important question of what services are “unrelated” to an ensuing admission. If hospitals do not use Condition Code 51 for such nondiagnostic outpatient services, CMS will consider the services related to the inpatient admission and not separately payable. This policy will take effect beginning April 1, 2011 and hospitals may add Condition Code 51 to outpatient claims dating from June 25, 2010. Hospitals may continue to bill ambulance services and maintenance renal dialysis services as separate services, while diagnostic services furnished within the payment window will be considered related. The transmittal is available by clicking here.