How do I use my warranty when repairing?

Posted by HREisGrrrrrrrreat@reddit | askcarguys | View on Reddit | 34 comments

Let's say my transmission broke at 20k mi, but my warranty covers bumper to bumper for 50k and I go to the shop, how would they know that my car is still under warranty or not? Is there something I need to have physically and show them in order for the warranty to work?

If so, what do I need?