Legal Question in Family Law in California

Nothing happens if you are late turning it in except that if it is so late that the judge or neutral doesn't have time to read it, you will waste a lot of time at the MSC going over things that should have been covered in writing ahead of time.

As an additional note, you cannot simply agree to continue a Mandatory Settlement Conference date. MSC and Trial dates are set by the court.

It depends on the judge. The court rules allow a judge to issue monetary sanctions for failure to timely file an MSC brief, or to fail to file one at all. Some judges are hard asses about it, and will issue sanctions. Many judges are nicer, and feel that issuing sanctions hinders settlement.