By federal law, as listed in the ADA, you do not need a prescription to have and use a service dog. So long as they provide just one task for someone with one disability. You do not even have to register them. The laws are changing constantly, and I recommend to learn more, that you go the the ADA and speak with your local representative. They are usually very welcoming, and willing to answer questions regarding the use of service animals in the US. If your employer needs a prescription, I would reflect to the ADA, but also to attempt to find another doctor to work with as well. I tried to link the ADA in one of my articles, but it got flagged. ADA stands for the Americans disability act. There is an office that is linked, but every state names their office differently. Coincidentally I am in North Carolina, and we go to the health department, Division of Vocational Rehabilitation Service. I know it has been awhile since you asked your question, but I hope others with similar questions may find this information helpful.