In the hubbub over the physician fee schedule, PPS changes and therapy cap drama, don't forget one major billing requirement in the New Year -- including National Provider Identifier numbers on your claims. All Medicare Administrative Contractors (MACs) are already rejecting claims if they can't validate NPIs used in NPI/legacy number pairs against the NPI crosswalk, CMS said in an e-mail message to providers. Durable medical equipment MACs began rejecting such claims Oct. 29. Starting Jan. 1, contractors will also reject claims without an NPI in the primary provider fields, CMS says. Those are the billing and pay-to fields. New deadline: For the time being, providers will still be able to use legacy-only numbers in secondary fields, such as the one for referring physicians. However, by May 23, providers will have to use NPIs in those fields as well, CMS says. And don't forget to make sure your referring doctors' NPIs are in line too. More NPI information is online at http://www.cms.hhs.gov/NationalProvIdentStand/.