Here's the text of Ontario's Highway Traffic Act: https://www.ontario.ca/laws/statute/90h08#BK232 https://www.ontario.ca/laws/statute/90h08#BK232 “The driver o

Here's the text of Ontario's Highway Traffic Act: https://www.ontario.ca/laws/statute/90h08#BK232 https://www.ontario.ca/laws/statute/90h08#BK232 “The driver or operator of a vehicle upon a highway, before turning to the left or right at any intersection or into a private road or driveway or from one lane for traffic to another lane for traffic or to leave the roadway, shall first see that the movement can be made in safety, and, if the operation of any other vehicle may be affected by the movement, SHALL GIVE A SIGNAL PLAINLY VISIBLE TO THE DRIVER OR OPERATOR OF THE OTHER VEHICLE OF THE INTENTION TO MAKE THE MOVEMENT." I guess one reading of this suggests that you must first check if it would be safe to make a maneuver, and if so, then and only then, must you use a turn signal. I think you could also read this as requiring safety checks and indicating (in either order) before turning, but I'm not a lawyer. I can't imagine that people are actually prosecuted for signaling out-of-order though. The driving handbook, however, tells you to check your mirrors, then "Signal that you want to move left or right." (here: https://www.ontario.ca/document/official-mto-drivers-handbook/changing-positions https://www.ontario.ca/document/official-mto-drivers-handboo...) which seems to suggest some level of intention-indicating is okay.