If it is obvious what service the dog provides, then staff at a public establishment may not make any inquiries regarding your disability or what your service dog is trained to do.

For example, if the service dog guides a visually impaired person or is pulling a wheelchair, it would be obvious what the individual’s disability is and what task the service dog is trained to perform.

If it is not obvious what service your animal provides (for example, if you have a psychiatric service dog), then staff members are allowed to ask only two questions:
• Is the dog a service animal required because of a disability?
• What work or task has the dog been trained to perform?

Under the ADA, inquiries from staff members must be limited to the two questions noted above. They cannot ask you what disability you have, nor can they ask you to have your service dog demonstrate the task they have been specially trained to perform.

If it is obvious that your service dog is a service animal that is helping with your disability, any inquiry regarding your condition is not allowed. You have no obligation to respond to questioning, and you can inform the questioner that they are violating your right to privacy under the ADA.
If it is not obvious what task your service dog has been trained to perform, the staff member can ask the two questions noted in FAQ 1. You do not have to give any further information or elaborate on your answers.
You may also, at your election, use ID cards, service dog registration information, certificates, harnesses, tags, vests and other accessories to help demonstrate that your dog is a service dog to prevent people from making intrusive inquiries in the first place.

There is no service dog specific registration requirement under ADA rules. Service animals are however subject to local dog licensing and registration requirements. Entering your service dog in our registry is done on a completely voluntary basis for your convenience.

Many service dog owners carry identification cards, registration information, or certificates and use tags, vests, and harnesses in order to signal that their dog is a working animal. 

Under the ADA, these items are not required for a service dog to gain access to public areas and do not confer any rights. The Department of Justice does not recognize certification or registration documents as proof that a dog is a service animal. Service dog owners commonly use these accessories to visibly inform members of the public and to curtail intrusive inquiries regarding their disability or service dog.