Microchipping and registering your cat: how it works
Lots of people think a cat that never goes out does not need a microchip. The law says otherwise, and so does experience: indoor cats slip out through a window or a moment's carelessness, and when they turn up, the chip is the only thing that leads back to you. But only if it is properly registered.
What it actually is
It is a tiny capsule, about the size of a grain of rice, implanted under the skin; in cats it usually goes on the left side of the neck or between the shoulder blades. It has no battery, sends out no signal and is not a GPS tracker: it cannot tell you where your cat is. All it holds is a fifteen-digit number. When a vet, a rescue or the police pass a scanner over it, that number comes up, and looking it up in the identification register leads to the details of the person responsible for the cat. That is the whole secret, and it works extremely well.
It is compulsory, indoor cats included
In Spain, Law 7/2023 (the animal welfare law) requires every cat to be identified with a microchip before six months of age, and most regions already required it under their own rules. It makes no difference if the cat never leaves the house: the obligation applies to all of them. And it makes sense, because indoor cats get lost more often than people think: an open window, a door left ajar, a house move, a carrier that pops open at the vet's. An indoor cat that escapes is usually terrified, hides close by and will not let anyone pick it up, and when someone finally does, the chip is the only way to know who it belongs to. Under Spanish national law, failing to identify your cat is a serious offence. Elsewhere, check the rules where you live.
How it is fitted and what it costs
A vet implants it with a needle slightly thicker than a vaccine needle, in one quick movement the cat barely feels beyond a prick. No anaesthetic is needed. It is usually done at one of the kitten's first visits, alongside the vaccines, or during neutering while the cat is under anaesthetic anyway. In Spain, fitting it and registering it costs €30 to €50 depending on the clinic and the region, and if you adopt from a rescue it normally comes included in the adoption fee. If you buy from a breeder, the kitten should be handed over already chipped: never accept a “you can get the chip done later”.
Registration, the step people forget
Fitting the chip and registering it are two separate things. The chip is only useful if its number is linked to your details in the pet identification register (in Spain, each region keeps its own). The vet who implants it usually handles the registration, but it is worth checking that it has been done, and in whose name. A cat with a chip that is not registered, or that is registered to the rescue, the breeder or a previous owner, is a cat that, if it gets lost, leads to nobody who can collect it. Always ask for the registration certificate or proof of registration in your name.
When you adopt or take on a cat
When a cat changes hands, the registration has to change too. If you adopt from a rescue, they should process the transfer of ownership into your name: check that it has been done. The same goes if you buy from a breeder. And if you take on a relative's or a neighbour's cat, do the transfer of ownership together with a signed transfer document, which is a simple formality at the vet's. If you find a cat in the street, the first step is not to keep it but to take it to a vet to have the chip scanned: there may be a family desperately looking for it.
Keeping the details up to date
A chip with an old phone number is almost a useless chip. If you change your mobile number or your address, update the details on the register; in Spain this is done through your vet or, in some regions, through the official college of vets or directly online. Add two contact numbers if the register allows it. And if your cat goes missing, Spanish law requires you to report the loss within forty-eight hours at most: doing so also flags the chip as lost on the register, so you can be traced quickly when someone scans it. If the cat dies, that has to be reported too.
Chip and collar: be careful with cats
For dogs, combining the chip with a tag on the collar is recommended. For cats, a collar has its risks: a cat can get it caught on a branch or a fence, or get its own leg or jaw stuck in it while trying to take it off. If you want to put a collar with your phone number on a tag, make it a safety collar, with a breakaway clasp that opens if the cat pulls hard, and fitted properly, with room for two fingers underneath. But it does not replace the chip: a collar can be lost, a chip cannot. For an indoor cat, a properly registered chip is the essential form of identification; a collar is an optional extra.
Microchips for travel and cat flaps
If you are going to travel outside Spain with your cat, the chip is the first requirement, before the passport and the rabies vaccine. And the order matters: the chip has to be fitted before, or on the same day as, the rabies vaccine, because a vaccine given to a cat that is not yet identified does not count for travel. The chip also has a practical use at home: there are cat flaps and feeders that only open when they read your cat's chip, very handy when several cats are on different diets or when you want to keep the neighbour's cat out.
Common questions
The chip does not wear out and never needs replacing: it lasts the cat's whole life. It can shift a little under the skin, which is why the vet scans several areas, but it does not get lost. Complications are extremely rare. It cannot be used to locate the cat: for that there are GPS trackers that attach to a collar, which are a different thing, and in cats they have the same drawbacks as any collar. And if you do not know whether your cat is chipped, for example because you adopted it as an adult or found it, any vet can check in a moment with a scanner.
In Spain, a microchip is compulsory for every cat before six months, including those that never go out. Check that it is registered in your name with your current phone number, update it whenever anything changes, and if your cat goes missing, report it within 48 hours. If you use a collar, make it a safety collar.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.