If my company pays me severance in a lump sum am I responsible for paying a portion back when I find a job if it's before the severance time? eg. 6 months severance but find job at 3? I'm in Ontario.

No, you are not responsible for paying any severance back, unless there is a specific term in your severance agreement that would require payback. Those terms are rare. If you have not yet signed off on any kind of severance agreement, it is always important that you have a severance offer or payment reviewed by an employment lawyer. Please give us a call at the number below if you would like to discuss the severance offer in more detail.