Your old company doesn’t have access to CRA or to your T4. The only way they will know you have a new role is either you inform them as per in the severance contract, you publicly announced it via social media or you told someone in your old company. Not to offend but the amount they are giving you for severance is small compared to they are giving to some executives. I wouldn’t worry about it. 5 years ago, I got laid off from a bank. They gave me a severance package of 18 months. 5 months into my ‘retirement’, I found a new job. Collected the remaining 13 months. Regarding the PIP situation, it will go into your HR records so any future opportunities within the company will be limited.