Why do dogs need collars?
It is important for your dog to wear a collar so there is somewhere to hang your dogs ID tag with your name, address and telephone number just in case your dog gets lost.
This became law in 1992 under The Control of Dogs Order 1992 if your dog was on a highway or in a public place. In 2016 every dog also now needs to be microchipped, but it is important to have the ID tag as well.
Another reason to wear a collar is in case you need to grab your dog in an emergency.