I think it's already a legal requirement for dogs? We had a right kerfuffle at the vets on her first appointment when we got the doggo because the breeder gave us the wrong documentation for her chip, mixed it up with another pup from the same farm (an actual farm, not a puppy farm
). I think she's actually about 3 weeks younger than her documents say as well
. But yeah it was a pain registering the chip she actually has. But yeah, I think it's a legal requirement for pups to be chipped BEFORE sale from a breeder, and so vets have to ask questions if you come in with an unchipped dog.
With the cat I'm sure it was only like £5 because they were running some local "get your cat chipped" scheme at the time.