A permission form is a document that you need to sign in order to allow someone or something to do something. It gives your approval or consent for that person or thing to take a specific action. Full definition
And, yes, I do have signed permission forms from each child's parents! (lauracandler.com)
We may include certain health information in e-mails that we send to you if you have signed an e-mail permission form. (plannedparenthood.org)
Drivers are, however, required to get permission form the courts to attend defensive driving classes for the purpose of dismissing a traffic ticket. (dmv.com)