Identity tags are still common place but more and more pet owners are using ID chips inserted bewteen the shoulders, either at intial vaccination or often at speying or castrating (when the little one is asleep). The chip and your pets details are then registererd to your address and kept by a computer firm for 30 years. If your loved one should go missing, simply scanning the chip and making contact with the computer company should re-unite both of you very quickly, but not before some worry has been endured for sure.
If you have move house, please remember to contact the computer records company to advise them of your new address. Should you lose your pet at any time, contact and attempted return will be made with your old address and proving ownership can be quite time consuming. There should be a change of address form with the original chipping paperwork you received when your pet was first chipped.
The basis of all travel schemes and exporting animals now relies upon chipping your pet.
Some of the newer types of dog / cat flaps use this ID technology to allow your pet(s), and ONLY your pet(s) access to your home.
If your pet is not chipped, ask your veterinary surgery for full details.