There si not a required certification program for service dog certification. In the United States you do not have to have an animal certified or trained specifically through any agency or program. Additionally, a service animal does not have to be trained from puppyhood. There are plenty of service dogs from shelters that are adopted as adults.

There are different rules for flying with an emotional support animal than for a service animal but they primarily involve the amount of time that an airline needs to be notified before flight.

Some states allow a landlord to ask for a letter from an MD stating that a service or companion animal is needed-but that varies.