The Control of Dogs Order 1992 says that all dogs when outside (subject to a few exemptions) must wear a collar with the name and address of the owner inscribed on it or on a plate or badge attached to it. We strongly recommend that you also put your telephone number on it. Any dog without this identification may be seized by the local authority and treated as a stray. The person in charge of the dog and/or the owner of the dog may be prosecuted leading to a fine of up to £5,000.
Although it is not a general legal requirement yet, Dogs Trust strongly recommends that (in addition to complying with the collar & tag law) all dogs should be microchipped.
What should I do if my dog strays?
Immediately contact your local Dog Warden through the Environmental Health Department of your local Council. In addition, if you believe that your dog has been stolen, then you should also report the theft to the Police. If the dog is found the Environmental Protection Act 1990 provides that the Council may sell, rehome or put your dog to sleep if it is unclaimed for a period of 7 days and their due fees aren't paid in full.