@michallis Where it belongs!
Also – VERY IMPORTANT. I noticed a little while ago on one of my truck renders that even though only a shadow appears “on the ground”, the white solid ground plane is still reflected in the vehicle’s chrome and paint – oops! I’ve spent the last like two hours trying to search the internet for a solution to this, but I found the actual fix by experimenting.
In the same section in the Object properties where you tick the “Shadow Catcher” box, UN-tick the “Glossy” box. I honestly could not tell you why this works, but it does.