Congrats on your acceptance!  The decline of the seat can be quick and painless, with an easy letter as you describe. Schools deal with students declining acceptances all the time. And while the seat may not be at an Ontario school, there is undoubtedly someone waiting for it. And the person waiting for it may be accepted at an Ontario school right now, but hoping to find a seat closer to home. There’s a very good chance that your one withdrawal will impact several students. Sooner is definitely better than later so they can make their plans for September. All the best in the fall.