What the certificate actually is
Article 10 refers to a clause in the wildlife trade regulations that control species threatened by trade. For animals on the most protected list, the law says they cannot be used for commercial purposes — sold, offered for sale, advertised, or displayed for gain — unless an official certificate covers that use. The certificate is issued by the government wildlife licensing authority, names the species, and identifies the individual animal or the transaction it covers. For tortoise keepers it is the single most important piece of paperwork an animal can have, because without it a protected tortoise generally cannot change hands legally for money.
Which tortoises it applies to
The certificate matters for tortoises in the highest protection category, the group usually called Annex A. In ordinary pet keeping that chiefly means three familiar species: the Hermann's tortoise, the spur-thighed tortoise (often called the Greek tortoise), and the marginated tortoise. The Egyptian tortoise is on the same list. Popular species in the lower category, such as the Horsfield's or Russian tortoise, are treated differently and do not need an Article 10 certificate to be sold, though sellers should still give you proper proof of origin. If a species is Annex A and money is changing hands, assume a certificate is required until you have confirmed otherwise.
The two kinds you will come across
A transaction-specific certificate covers one particular sale of an animal that cannot yet be individually identified — typical for hatchlings too small to microchip. It is used once, for that sale. A specimen-specific certificate is tied to one identifiable animal, usually once it is big enough to be microchipped, and it stays with that tortoise for life: every future sale should pass it on, so the chain of paperwork follows the animal from keeper to keeper. When you buy a larger juvenile or adult of a listed species, the specimen-specific certificate is the document you should be handed.
What to check before money changes hands
Ask to see the certificate before you commit to buying a listed tortoise, and check that the species named on it matches the animal in front of you. For a specimen-specific certificate, the microchip number on the document should match the chip scanned in the tortoise. Walk away from a seller who offers an Annex A tortoise for sale with no certificate and a vague story — the paperwork problem becomes yours the moment you pay, and it can make the tortoise impossible to sell, breed from commercially, or even insure later. If a certificate has been lost, the licensing authority can advise on replacing it; sorting that out is the seller's job before the sale, not yours after it.
Keeping the paperwork straight afterwards
File the certificate with the tortoise's purchase receipt, chip details, and a photograph of the shell pattern, and keep a scanned copy somewhere separate from the original. If you later sell or rehome the tortoise, the certificate goes with it as part of the handover.
Storing the certificate details inside KinsLe's Pet Passport keeps a tortoise's legal paperwork, identity, and health notes in one packet that can be produced whenever a buyer, vet, or insurer asks.