Although every state has its own unique laws regarding child support in a divorce case, most use a similar system to decide who has to pay. Section 4055 of California's Family Code has the state’s formula for determining child support. It uses the amount of both parents’ income to be allocated for child support, the higher earner’s net monthly disposable income, the percentage of time the higher earner will have primary physical custody of the child compared to the other parent and the total net monthly disposable income of both parties.
The parent with a higher net monthly disposable income will be responsible for paying child support, in most cases. The equation will also determine the amount, which will be a reasonable number based on how much the parent makes and what the child requires in expenses. If the mother is the higher earner out of the two parents, he or she will have to pay child support.
If the mother is the higher earner and has primary custody, this may mean that she is responsible for a greater portion of the childcare expenses. If the mother does not have primary custody, she may have to pay the father a certain amount in child support each month to bridge the gap between what either parent spends in child care.