A Business Number (BN) is a 9-digit unique number provided by the Canada Revenue Agency (CRA) to use as an identifier when conducting business with federal programs and services. It is an official identifier for taxes and government submissions like GST/HST, payroll withholdings, and corporate tax on income. When you create a new business or Ontario corporatin, you may receive a BN automatically. Alternatively, you can request one directly from the CRA. The number remains with your business forever, regardless of a name or address change.