A microchip is a rice-grain-sized transponder injected under your pet's skin, usually between the shoulder blades. It carries a unique 15-digit number that a scanner reads in seconds and links to your contact details on a database. It is cheap, essentially painless, lasts for life — and for dogs everywhere in the UK, and cats in England, it is the law.
The law for dogs
Compulsory microchipping for dogs arrived in England, Scotland and Wales on 6 April 2016 (Northern Ireland led the way in 2012). The rules — now consolidated in England under the Microchipping of Cats and Dogs (England) Regulations 2023 — say a dog must be:
- Microchipped by eight weeks old, before it is sold or rehomed;
- Registered on a compliant database, with the breeder recorded as the first keeper;
- Kept up to date — the current keeper's name, address and contact details must be correct on the database at all times.
The breeder must chip and register the puppy before sale. When you buy, the chip is then transferred into your name — you become the "keeper" on the database. A breeder who hands over an unchipped puppy is committing an offence, and it is one of the clearest red flags in our guide to buying a puppy safely.
The law for cats in England
Since 10 June 2024, all owned cats in England must be microchipped and registered by the time they are 20 weeks old. The rule applies to indoor cats too — a cat that never goes out can still slip through a door, and unchipped strays are the hardest animals for shelters to reunite. Free-living feral and farm cats without keepers are exempt.
Scotland, Wales and Northern Ireland have not yet made cat microchipping compulsory, though it remains strongly recommended everywhere and most rescues chip every cat before rehoming.
Fines: what "up to £500" actually means
If your dog (anywhere in the UK) or cat (in England) is found without a chip, or with out-of-date details, enforcement bodies can serve a notice giving you 21 days to comply. Ignore it and you face a fine of up to £500 — and the chip can be implanted at your expense. In practice enforcement is complaint-driven and reunification-driven: the fine usually surfaces when a stray is scanned and the details lead nowhere.
Out-of-date details are the silent failure. Around a third of strays scanned by rescues carry chips pointing at old addresses or dead phone numbers. A chip with stale details is nearly as useless as no chip at all — update the database every time you move or change number.
Compliant databases
Not every pet database counts. The details must sit on a DEFRA-compliant database — the government publishes the current list on GOV.UK, and it includes the largest operators such as Petlog, Identibase, Animal Tracker and MicroDogID among others. Compliant databases must answer lookups from vets, councils and police, and pass details between each other when a pet is transferred.
If you are not sure where your pet's chip is registered, enter the chip number at a check-a-chip lookup service (your vet can scan for the number for free) and it will tell you which database holds the record.
What to check when buying or rehoming
Whether you are buying a puppy, a kitten, or an adult pet, run through this list before money changes hands:
- Ask for the microchip number and check the paperwork shows a compliant database.
- Ask the vet to scan at the first check-up and confirm the number matches the documents. Mismatched chips are a hallmark of smuggled puppies.
- Confirm the breeder is the first registered keeper. For puppies, the breeder must appear as the original keeper on the database — a different name suggests third-party dealing, which is illegal for puppies and kittens under Lucy's Law.
- Never accept "you can chip it yourself later" for a puppy — the seller has a legal duty to chip before transfer.
Rescue animals come chipped almost universally; the rescue will handle the transfer as part of the adoption. That reliability is one of the practical advantages we cover in adopting vs buying.
How transfer of keepership works
Transferring a chip is straightforward, but it is the new owner's job to see it through:
- Get the chip number and the database name from the seller.
- Contact the database (nearly all handle it online) and request a transfer of keepership. Some databases let the previous keeper initiate it; either way you confirm and complete it.
- Pay the small admin fee — typically £3 to £20 depending on the database, with some offering free lifetime updates as a premium option.
- Check you receive confirmation that your name, address and phone number are now on the record.
Keep the confirmation email with your pet's paperwork. If a dispute ever arises about ownership, the database record is one of the first things anyone will look at — though note the registered keeper is not automatically the legal owner; receipts and contracts matter too.
The bottom line
Microchipping is the cheapest insurance you will ever buy for your pet: a one-off £10–£30 that turns a lost animal into a found one. Chip by the deadline, register on a compliant database, and update your details every time life changes. When you are browsing dogs or cats on PetHome, treat the chip paperwork as non-negotiable — and if a seller cannot produce it, use the report button and read our pet safety guide before going any further.