Originally Posted by Robbie

You don't file any documents. I use a model release form and I shoot a picture of their ID.

Here in the U.S. that is what you have to keep to show to authorities under the US 2257 regulations. (basically the same thing we always did anyway before 2257)

There's a little bit of specific wording you want in there. But a search on Google should get you a template to start with and you can tweek it out to suit your needs from there.