As part of the Responsible Use of Magic decrees (RUM), Caretaker Ezzelin of Sundabar created the Licensing System. This required every spellcaster in Kildar to undergo a licensing exam in order to be allowed to cast any magic. This was done to register the Kildarian spellcasters and their abilities so that the Lords Alliance could keep better track of those who might imperil Kildar or the entire world with dangerous magic, such as what happened with the Reactivated Netherese Portal network.
Adventurers and other magic users can get their licenses through the Licensing Institutions. Those that get their magic through ways that the Lords Alliance sees as Unorthodox, such as those that derive their power from evil, chaotic or otherwise dangerous forces might find it very hard if not impossible to be approved for one however.
As part of your backstory or during the campaign, you can get a magic license for 10 GP if you are not a criminal to the Lords Alliance. It is illegal to cast spells anywhere in Kildar without possessing a license, but realistically this is only enforced in places with Lords Alliance guards. The licenses hold the persons full name, an identifiable drawing, the source of the persons magic and the Office that gave out the license.
If you are not keen on being on the Lords Alliance's records, or they not keen on letting you have one, you can ofcourse try to get away with a fake one, but only The Eldritch Inquisition Remnants have been able to make one that can reliably fool Lords Alliance Guards, and even these are not fool proof.
The license is legally required for any spellcaster that is able to cast Level 2 spells and above.