Am I required to pay college tuition as child support for my 20 yr. child?
In California, there is no statute or case law that requires a parent to pay child support, including secondary education past the age of 18. Many divorce agreements anticipate the desire or need for both parents to help their child pay for his or her college education. The courts retain jurisdiction to enforce divorce agreements. Therefore, if the payment of a portion of the cost of college tuition is part of the court orders, then the court may require such payment even though the child is past the age of majority.
The divorce decree may contain details about proof of college tuition expenses. If it does not, then you may consider asking your ex-spouse for copies of the tuition bills, book expenses, etc.
If she refuses or neglects to provide them, you may be able to obtain them directly from the school.