Sometimes called a registration, tax, "C," or resale number, the Unified Business Identifier (UBI) number is a nine-digit number used to identify persons engaging in business activities. The number is assigned when a person completes a Master Application to register with or obtain a license from state agencies. The Departments of Revenue, Licensing, Employment Security, Labor and Industries, and the Corporations Division of the Secretary of State are among the state agencies participating in the UBI program. In most cases, your UBI number will also be your DOR registration number. Spouses who wish to file separately and business entities who have divisions that wish to file separately will be assigned separate DOR registration numbers as needed.