If you're an employee, no need for a COR. You just need to file your Annual Income Tax Return (1701) but do make sure you have your 2316's from your employer/s with you. You'll need them as you fill out your 1701.
Otherwise, if you're a self-employed individual or professional, then yes, you do need a COR. This makes sure that the taxes you file are tagged against your TIN properly.
If you don't have a COR and you need help registering your business, we are piloting a service currently that can help you with that. Just send an email to our Biz Reg Team and we'll send you the details of this new service.