You worked hard for your business and your crew do a heck of a job keeping your vehicles clean, smelling nice and running well. So it’s understandable you may have a policy about pets in your cars.
Maybe it’s a strict no pets policy.
Maybe it’s an added fee, like an under 21 driver fee.
But what kind of policy is there when it comes to service animals?

There have been lawsuits on behalf of the handicapped who utilize service animals against rental car companies who have denied them services. It appears the reason for the lawsuits comes from lack of knowledge when it comes to the American with Disabilities laws as they relate to rental vehicles. Here is what you, and most importantly, your rental car staff need to know to provide the best customer service to your customers who have service animals.
First, the basic law itself.
The Americans with Disabilities Act of 1990 (ADA) prohibits discrimination and ensures equal opportunity for persons with disabilities in employment, state and local government services, public accommodations, commercial facilities, and transportation. It also mandates the establishment of TDD/telephone relay services. The current text of the ADA includes changes made by the ADA Amendments Act of 2008 (P.L. 110-325), which became effective on January 1, 2009. The ADA was originally enacted in public law format and later rearranged and published in the United States Code.

What this means to a rental car company:
Simply put, you cannot deny a service animal from getting into your vehicles. …the ADA requires public accommodations to make reasonable modifications to their policies and practices as necessary to afford their goods and services to persons with disabilities, as long as doing so does not fundamentally alter the nature of their goods and services…”

You cannot deny service animals from getting on any conveyance offered by your company that moves your customers from point A to point B (example: from the airport to your rental facility.)
…shall allow persons with disabilities the use of service animals under the ADA, including guide dogs, signal dogs, or other animals individually trained to do work or perform tasks for the benefit of an individual with a disability”…shall not require people with disabilities to provide any type of identification or certification of an animal as having been trained as a service animal… shall not require persons with disabilities to be separated from their service animals at any time.” The rulings stated above, though enacted against a large rental car franchise, also pertains to the local market. You may look at your neighborhood and think service animals do not, or will not, pertain to your business….there is always a first time for everything.

http://www.ada.gov/budget.htm