Id say its a good idea, had an english bull terrier bitch 10yrs ago, that had the ear tattoo, I sold her on and told the new owners it would cost £10 to have the name of ownership changed over, god knows how many hands she went through in those 10yrs, but battersea got in touch with me around 8 months ago, saying that they had my dog, looks like she's been through the wars a bit, she'd had a full hysterectamy (cant spell) when I had her, but now has arteritas in back legs, and battersea removed a few cancerous lumps, shes now on medication for life, but we have her back, all due to the ear ta