When Your Child Turns 18: Is the Last Month of Child Support Pro-Rated?

Your child turns 18 on the 5th of the month. Do you owe child support for the whole month, or just those first five days?

The short answer in California: you owe the full month. Child support is not pro-rated for the final month, even if support ends a few days in.

Why the last month isn't pro-rated

Most child support orders set a monthly amount that is due on the first of the month. If support is owed on that first day, the whole payment is owed. Nothing in California's statutes or court rules provides for splitting that final payment by the number of days.

The local child support agencies apply it the same way. If even one day of support falls in a month, they treat the full monthly amount as due. Family law attorneys around the state report the same approach in court.

The flip side is that the paying parent doesn't owe anything for the following month, as long as support has actually ended.

First, make sure support actually ends at 18

This is where many parents get tripped up. In California, turning 18 does not automatically end child support.

If your child is 18, unmarried, still a full-time high school student, and not self-supporting, support continues. It ends when your child finishes 12th grade or turns 19, whichever comes first. A child with a summer birthday who graduates the following June can easily be owed several more months of support.

Your own order or agreement may also say something different. Some parents agree to continue support through college or set a specific end date. Read your judgment before assuming support stops on the birthday.

Practical Tips

Put the end date on the calendar early. Know the birthday, the expected graduation date, and what your order says, so the last payment isn't a surprise to either parent.

Stop wage garnishment the right way. If support comes out of a paycheck, the employer won't stop it on its own. The withholding order has to be terminated, or you may keep paying after support ends and have to chase a refund.

Remember that past-due support doesn't disappear. Any unpaid support from earlier months is still owed after the child turns 18 or graduates.

If you have more than one child, the amount usually goes down rather than ending. Support for the remaining children is generally recalculated, and that may require a new order.