Legally, you can terminate for any reason in Ontario - you may have to pay severance if it is without just cause, but you can always terminate an employee (barring, of course, obvious illegal prejudices). You are also within your right to ask for more than an open-ended doctor's note. Are there risks if you terminate the employee while applying for STD? Absolutely! Even an employee who was on a performance improvement plan? Absolutely. There is a chance it is viewed by courts as a reprisal. There is a chance, especially if the leave is related to anxiety or depression, that the work conditions impacted the employee's mental and physical health and thus forced the employee to deliver a sub par performance and ultimately led to a disability - at least that is the perspective I would leverage if I were the employee's legal counsel. So where does that leave you as an employer with doubts about the legitimacy of the STD claim of a sub-par employee (which is the sense i get from the question)? Answer: not in the ideal situation. What advice can we give you? First of all, an STD claim has been filed and the employee is on unpaid leave, so you are not at a financial loss. You could hire somebody better to replace that position, but if the STD is approved, at it's conclusion you will have to create a return-to-work plan and effectively hire back the employee. If you don't readily have an open slot for that employee you may have the financial burden of too high a headcount for a period of time, or you may have to make room for that returning employee. But maybe, the employee in question will come back ready to work, maybe the medical issue was impacting performance and you will have an engaged and active employee at the end of the STD (that's the hope anyways). If, however, the STD is denied, you then have an employee with performance issues (hopefully very well documented) that has made an STD claim that was deemed by a 3rd party as not having merit; this would be a pretty strong case for termination. It may not be the advice you wanted to hear, but you are better off letting the STD claim play out before making any moves, no matter what you may be thinking about this employees motivations or behaviour, because ultimately, your feelings are not facts. You may be right, and odds are that you probably are because you know your business far better than I do, but still, your feelings are not facts. Trust me when I say that as much as it stings to sit and wait for this to play out, it will sting so much more if you act and have to pay extra after litigation, and extra-extra if you were wrong in your perception of the situation and motivations.