Legal Question in Family Law in California

Child support is calculated not only on incomes but on custodial time. The formula is so complex that you are required to calculate it and submit reports to the court on court approved computer programs, although pretty much everyone uses Dissomaster. The heart of the formula, however, is not TOO complex. Basically, the complex part of the formula figures out how much each parent owes the children, primarily but not ONLY based on income. We say "owes the children" because child support is considered owed to the children (total fantasy, but it's the policy of the state to look at it that way). Once the monthly amount each parent owes the children is determined, however, the rest is fairly easy. Each parent is considered to have spent their share while the children are with them and owe it while the children are not. So if one parent owes $1000/mo to the children and has 90% custodial time, they are considered to have spent $900 on the children and owe $100. If the other parent owes the children $500/mo and has 10% custodial time, they are deemed to have spent $50 and owe $450. The last step is to deduct the lower number from the higher, and the parent with the lower number gets the difference as child support. So in that scenario, even though the high earner presumably had somewhere around twice as much income as the lower earner, the lower earner owes $350/mo child support to the high earner. The question in your friend's case, however, is was there an order that she pay support, that she then didn't pay? Back child support is generally only owed from when the receiving parent files a motion or Order to Show Cause seeking support. So unless there is an 8 year old support order that she has not been paying, she will only owe support going forward.