What a dog's microchip actually proves

A breeder hands over a puppy and, somewhere in the paperwork, a fifteen-digit number. Scan it and a name and address come back. It feels like proof — an identity fixed in place, independent of whatever anyone in the room happens to say. It is a pointer to a record. Whether that record is true is a separate question, and it is the one that matters.

What the law actually requires

Every dog in England has had to be microchipped since 6 April 2016, under what was then the Microchipping of Dogs (England) Regulations 2015. Those regulations were revoked and replaced in 2023 by the Microchipping of Cats and Dogs (England) Regulations, which kept the dog rules in place, brought cats into the same regime from 10 June 2024, and tidied up the database standards that sit behind both.

The obligation that matters most for a buyer falls on the breeder, not the new owner. The breeder — specifically, whoever is the registered keeper of the bitch — is the puppy's first keeper in law, and must be recorded as such on an approved database before the puppy is eight weeks old. A breeder cannot skip that step and let the buyer register the chip in their own name instead; doing so is itself a breach of the regulations. The 2023 rules go further and tie the two events together directly — regulation 9 makes it a condition of lawfully transferring a dog to a new keeper that the dog is already microchipped. No chip, no compliant sale.

None of this happens on one central government database. The regulations set minimum standards that several commercial operators — Petlog among them — have to meet to be classed as an authorised database, and a breeder's choice of which one to use is not something a buyer can infer from the chip itself. The number identifies the chip. Which database holds the record behind it is a separate lookup.

What the chip proves, and what it doesn't

A scan proves that a specific chip, implanted in a specific dog, is linked to whatever contact details someone typed into a database at some point — the breeder at implantation, most often, or a later keeper who updated the record after a sale. It does not verify that those details are current, that the person named is who they claim to be, or that the chain of custody since implantation has been recorded at every step. The system depends entirely on people doing the paperwork, and the evidence is that a great many don't.

Battersea surveyed fifty UK local authorities on the stray dogs they collected in 2026 and published the results in July. Thirty-two per cent of those dogs weren't microchipped at all, a decade after the law made it compulsory. Of the ones that were chipped, thirty-four per cent carried details that were out of date. And across the survey as a whole, eighty-seven per cent of stray dogs could not be reunited with an owner using the chip alone — missing, wrong, or unreachable details accounting for most of that gap, on top of the dogs with no chip to begin with. Not a fringe failure rate, but the ordinary outcome for most strays, chip or no chip. The same research found that a dog with current, accurate microchip details is more than four times as likely to be reunited as one without. The technology works. The data behind it, routinely, does not.

For a buyer, the practical version of that gap is this: the chip number on a puppy's paperwork tells you a chip was implanted and a record exists. It does not tell you the breeder registered themselves correctly as first keeper rather than leaving the field blank or entering someone else's details, and it does not tell you the database will still hold accurate information in three years, when accurate information is exactly what you'd need if the dog ever went missing.

What to actually check, and when

Ask to see the chip scanned in front of you, not just quoted from a certificate — a number on paper proves nothing about the dog standing in the room until a reader confirms the two match. Ask which database holds the record and whether the breeder is named on it as first keeper, which the regulations require and which a legitimate breeder should be able to show without hesitation. Once the puppy is yours, update the keeper record yourself, promptly — the obligation shifts to you the moment the transfer happens, and a chip registered to a breeder who sold the dog six months ago helps nobody if your dog goes missing in the meantime.

None of this replaces the other checks covered elsewhere in this journal. A chip is not a health record — see what good health testing actually looks like for that. It is not proof of registration pedigree, which what KC registered actually means covers on its own terms. And on the wider question of what a breeder owes a buyer before Lucy's Law ever enters the conversation, post-Lucy's Law: what buying from a breeder actually looks like now sets out the rest of it. The horse-world version of this same gap between an official document and the facts it's assumed to settle is in what a horse passport actually proves — the detail changes, the lesson doesn't.

Why this sits on a marketplace's conscience

We didn't build GenoVaq's verification around the microchip number, for the same reason we didn't build it around a passport or a certificate on its own: a reference number is only as good as the record it points to, and nobody checks that record is still accurate between the day it's created and the day someone needs it. What we ask for instead is the paper trail around the chip — who registered it, when, and whether the breeder can show the puppy was theirs to register — which is closer to the question a buyer is actually trying to answer. That's the same discipline behind the free lifelong health record described in why we built a free health record: the value isn't in the number itself, it's in someone keeping it current after the sale, which is the part the law requires and the part that keeps lapsing.

A chip is worth having. It is not worth mistaking for an answer.

---

Sources

• The Microchipping of Cats and Dogs (England) Regulations 2023 — legislation.gov.uk
• The Microchipping of Dogs (England) Regulations 2015 — legislation.gov.uk
• Information for dog breeders — South Tyneside Council
• Microchipping at an all-time low — Battersea Dogs & Cats Home
• About microchipping — Petlog

— Rene