A business number is a nine-digit number used to identify your business in communications with the government. For example, if you collect GST/HST, you need a business number to submit your GST/HST payments to the Canada Revenue Agency. Not all businesses need business numbers, but they are required in many cases. If you decide to incorporate your business, it needs a number. In addition, if you have employees, collect sales tax, or deal with imports or exports, you also need a business number. Your business number becomes part of your program number. For example, when you hire your first employee, you have to sign up for a payroll account with the CRA. Your program number consists of your business number, two letters to represent payroll, and a four-digit reference number. To register for a business number online, you need your Social Insurance Number, your business name and address, and the SINs of any other owners. If you have just incorporated, you also need incorporation documents. You may need information related to the specific program you need to use. For instance, if you’re signing up for the payroll program, you need details on your employees.Many businesses need a business number right away, but others do not. If you start out as a sole proprietor with no employees and not enough sales to pay GST/HST, you don’t need a number. As your business expands, you may need to register for one.