Legal Question in Family Law in California

Support can go back three years. Active duty military have some special procedural protections, but if you are really the dad, you will have to pay eventually.

If there is no proceeding, you are not going to be paying "back" child support for three (3) years. I don't understand where Mr. McCormick gets that number.

To get child support, the other parent, or the county, would have to file a paternity action against you, and prove paternity. The Family Code clearly states that child support can only be made retroactive to the date of the filing of the petition. If the parent ordered to pay child support (called the obligor parent) was not served with the petition within 90 days after the filing, and was not evading service) then the child support order will not be made retroactive any earlier than the date of service. (Fam. Code, sect. 4009.)

The reason for this is an incentive for the custodial parent to get moving and get a child support order in place, and file the petition, and not to sit back and rest on their laurels.