Pick what you need to do and who you are. This finder points you to the guide for that federal portal and to the official page for the portal itself. It does not decide whether you qualify for anything.
Where this comes from
The guides linked below are this site's own guides. The official pages are the Government of Canada services directory, the Canada Revenue Agency page on changing a GST/HST account, and the Corporations Canada page. If a portal has changed since the guide was written, the official page governs.