As of January 1, 2016, a French ordinance requires that anyone placing an advertisement to sell one dog or one cat are required to register as a breeder and supply a Siren business identification number. This number has to be written in all classified ads for selling dogs and cats. Siren numbers can trace directly to the breeder’s identity and contact information. Potential buyers can have access to the name and postal address of the seller. Classifieds sites in France have taken measures to prevent validation of a pet ad without a Siren business identification number. An algorithm should be able to detect any false Siren number. All sales profits (from the first animal sold) are subject to income tax and must be reported. The ordinance does not apply to individuals who sell a dog they bought, nor those who give their pets away. @BarbaraLapointe