my girls only wear collars on walks, and they weartheir martingales, exept for Electra who until she is older wears a buckle collar with her microchip tag on it. Happy and Misty each have 1 ID tag but neither have actually worn them in years, I dont even know where they are lol, but I am not worried about loosing Happy and Misty either, it would be more difficult to get rid of em in the first place I do have ID tags on then when someone else is watching them however, I trust them with ME not with other people. my moms always wear collars with 1 ID tag, I have never even considered more then 1 ID tag per dog lol