Child support question…

So say the father isnt helping supporting the mother and their 2 kids. He lives with his mom has a good job to give money to the mother of his kids. And he doesnt corporate with the child support system will not give the mother any money.. what happens to him? Does he get fines or has to pay her with no question?. And he threatens her of quitting his job that pays taxes to work somewhere under the table and hide.. lol smh. So he wont give her money basically.. dont really know how this all works… yeah the mother provides and does have a job but he has to help her right ? Even if they aren’t together or he doesnt even see the kids he has to help her or go to jail? I live in california by the way