August 20, 2020
You can use your application number from any Canadian medical school that uses CASPer to sign up. If you are only applying to Ontario schools, you can only write CASPer on the Ontario dates that start on October 7, 2020 (so you will have an OMSAS number when you register). Spaces are unlimited so it is not a concern to wait.
If you use an application number from a Canadian medical school outside Ontario, you will need to add your OMSAS reference number, once you receive it, in order to release your scores to Ontario medical schools.
For more information visit the CASPer website.