It's usually a state law isn't it, and they determine it, not local people? You fill out a form for the state and get the exemption status and then you can show that to the idiot local people if they have extra local taxes sometimes. I wouldn't even mess with locals other than sending them copies of whatever forms the law says (and if they're resistant, a copy of the law or page form the website describing it like this one in Ohio, and circle it in red

http://auditor.cuyahogacounty.us/commservices/FAQ.htm