When you formally change your legal name, you will need to update all of your government documents including your birth certificate. This can be a lengthy, costly, and for some a bit of an unnerving process. If you were born outside of Canada, you will require the marriage certificate after the wedding to make changes here. However, if you were born in Canada you can legally change your name any time you wish.
However, another option is to simply 'assume' a new name, rather than formally change it (and your birth certificate).
The distinction can be complicated. As often as I've tried to help with this topic, its always best to contact Service Ontario directly to discuss which option serves you and your needs best.
Take your marriage certificate, your current photo health card, and your driver’s license to a Service Ontario office to start the name change process. Search for your local Service Ontario location online.
When assuming a new name however, you should not use your maiden name and assumed married name at the same time, as this can cause confusion for financial or government agencies, and may result in difficulty for you.