CMS wants to remind practices that the new Medicare Beneficiary Identifiers (MBI) do not contain “Os,” but instead utilize zeros, eliminating any confusion on the matter. Nuts and bolts: Each unique MBI consists of 11 randomly-generated alphanumeric characters. CMS uses the numbers 0-9 and uppercase letters from A-Z in the MBIs, according to MLN Matters SE18006. Important: An exception to this rule is that the letters S, L, O, I, B, and Z are not included. CMS excluded these letters to avoid confusion. The percentage of claims using beneficiaries’ new MBI numbers continues to grow, too. For the week ending Jan. 25, providers submitted 62 percent of fee-for-service claims with the MBI number, CMS reports. “We encourage you to use MBIs now for all Medicare transactions,” the agency tells providers. Two weeks earlier, CMS had reported the percentage of claims using MBIs at 58 percent. See the MLN Matters guidance at www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNMattersArticles/downloads/SE18006.pdf.