https://www.mercurynews.com/2019/08/23/real-id-what-if-the-dmv-never-sent-me-that-letter-everyone-else-got/

More than 3 million Californians carrying REAL ID licenses were supposed to receive a form to sign and return, a simple fix for a documentation problem.

If you have a REAL ID that you applied for before April 30 and you haven’t gotten that letter yet, you should request one. Here’s how: