How Microchips Work to Reunite Pets With Their Owners
A scanned microchip only leads home if the details behind it are current. How the number, the database and the law fit together when a stray dog is found.
You've come across a frightened dog that isn't yours, and you want to do the right thing. In England, Wales and Scotland, a dog in public must wear a collar with the owner's name and address, either on the collar itself or on a tag. If it has one one, you can often return the dog that way.
If not, the next step is to get the dog to someone with a scanner: a vet, a rescue centre or the council's dog warden. They can scan the microchip and get the dog home.
How the chip itself works
A microchip is a passive device with no battery of its own, so it can't run down or be switched off. It stores a number and nothing else, and it can't be tracked. When a scanner passes over the dog, it powers the chip just long enough to read the number.
In England, a chip implanted in a dog must carry a unique number including the manufacturer's code, meet the ISO 11784 and 11785 standards and answer a 134.2 kHz FDX-B reader.
The chip sits under the skin between the shoulder blades, and implanting it takes a few seconds.
Where the chip number goes
The number links to a record held on a database, with the owner's name, address and phone number, plus the dog's breed, colour and date of birth. The chip is a permanent implant; the record is what can go out of date.
Pet Database's chip checker takes a 15-digit microchip number and searches multiple UK databases at once. It tells you whether a chip is registered and which database holds the record, but it never shows the owner's contact details.
If you're a dog owner reading this from the other side, Pet Database's dog microchipping page covers getting yours registered properly.
What to expect, and what not to do
If you've taken charge of a stray dog, in England, Wales and Scotland you must straight away either return it to its owner or hand it to the council's officer for the area where you found it, and tell them where. The full rundown of who to call is on Pet Database's found a dog page.
Don't assume the dog becomes yours just because nobody can be reached. In England and Wales, keeping it doesn't make you the owner, and the original owner can still claim it. Scotland is different: a finder who keeps the dog for two months without a claim becomes its owner.
How the owner finds out
For privacy reasons, a finder isn't given the owner's contact details. On Pet Database, vets, wardens and pet rescuers can look up the owner to make contact, while a member of the public never sees those details.
Pet Database also notifies the owner the moment a pet professional logs in to view their record. So if your own dog has been found, the call comes from the vet, warden or rescue holding them, using the phone number on your record. If your own dog is missing, see the first hour after a pet goes missing.
How a lost dog is reunited with its owner
If the owner can't be reached, the dog goes to the council's stray dog officer. In England, Wales and Scotland, that officer must keep a public register of seized dogs, open to inspection and free of charge at reasonable times. If the owner is identified, the officer must serve them a written notice saying the dog has been seized, where it's being kept, and that it may be disposed of if it isn't claimed and the fees aren't paid. After seven clear days unclaimed, the council may rehome the dog or pass it to a stray dog establishment. (In Northern Ireland the period is five days).
Collecting a seized dog isn't free. In England, Wales and Scotland, the owner can't take the dog home until they've paid all the expenses of its detention plus a further prescribed amount. That amount is £25. Councils then add their own charges, which vary. Merton Council, for example, lists the £25 statutory fee, a £120 collection fee, £30 for returning the dog from kennels and £36.96 per day for kennelling.
The true cost of finding a lost pet is worth knowing before it lands on you.
Finding the owner only works if the record is current. The dog charity Dogs Trust's 2024 to 2025 stray dog survey looked at chipped dogs reaching councils with a known result. Only about 31% had correct owner details, 56% had incorrect details and 12% had unregistered chips.
GOV.UK says the owner is responsible for keeping those registered details current, which matters when you move house or change your phone number. A record that still points to an old phone number ends up at the stray dog officer the same way as one that was never registered.
Common questions
Will I find out whether the dog got home?
Usually, no. The chain of calls is private, so you may not hear back. If you handed the dog to the dog warden, you can ask the council whether it was claimed.
Can I keep the dog I found?
Tell the council officer you want to keep the dog and give your name and address. They follow a set procedure and may let you take it. You'd then have to keep it for at least one month.
Does any of this apply to cats?
The finder rules in the Environmental Protection Act 1990 apply to dogs only, and give no period for cats. If you've found a cat, get it scanned at a vet or rescue the same way, and let them take it from there.
There's no council duty for stray cats, so the warden route doesn't apply. The dog and cat charity Battersea's 2026 survey of English councils found 99% provide no stray cat service and refer callers to local vets or welfare charities. If you can't get to a vet, a local cat welfare organisation may be able to come and scan the cat. Having a found cat scanned at a vet is free of charge, though there may be a wait.
The chain home starts with a scan and rests on whatever that finds. Check a chip against your own record now, so if your dog is ever the one found, the call reaches you and not an out-of-date record.
