Under the Canadian Business number, you must register for each program that you will be using. The most common program accounts a business will need are GST/HST, payroll deductions, corporation income tax, and import-export.
The First 9 digits of your number are your business number. The following two letters identify the type of program account. The last four digits are the reference number for a specific program account. As an example if you registered to be an importer and also registered for the GST/HST 999999999RM0001 would be an importer number and 999999999RT0001 would be a GST/HST number.