Your corporation is assigned two different numbers with somewhat confusing names: the Corporation Number and the Business Number. Both numbers are used for communicating with different branches of the government. Below are some tips on how to distinguish the differences between the numbers.
The Corporation Number
This number is assigned by Corporations Canada at the time the company is incorporated. It is used for filing legal documents with Corporations Canada (such as any changes in the Corporation's structure, or to file the Annual Return).
The Business Number
This number is assigned by the Canada Revenue Agency (CRA) within 1 or 2 business days of incorporation.
It is required to register for a GST/HST Account with the CRA, and is sometimes referred to as the HST or GST Number.
You will use this number in the future when interacting with the CRA for tax filing purposes.
Business numbers have a variety of endings/identifiers depending on the account. In each instance, the nine digit number remains the same, with the program identifier changing. For example:
Income Tax 123456789 RC 0001
Payroll 123456789 RP 0001
HST 123456789 RT 0001