My work permit expired, but I’ve maintained my status. Can I keep working under the same conditions of my initial work permit if my Social Insurance Number (SIN) is expired?
Yes. If you applied to extend your work permit before your initial work permit expired, you can keep working, even if your SIN is expired. This is allowed under the Employment Insurance Act and Regulations.
Renewing your SIN
When you get your new work permit, you can
renew your SIN.
You can give your employer proof that you’ve applied to renew your SIN. Once you get a new expiry date for your SIN, you must give it to your employer within 3 days.
Info from CIC website. You CANNOT extend/renew your SIN number without your extension being approved, though you can keep working if you maintained status.