Good question.
I cannot answer this question for how all jurisdictions would handle it, but I can tell you what the law is in Utah governing this question (and it’s a safe bet that most jurisdictions take a similar approach, but you will want to inquire with an attorney licensed to practice law in your jurisdiction, of course).
In Utah, here is how that would likely play out:
Let’s assume that before the award of primary physical custody of your children was taken from the other parent and awarded to you, you had a child support obligation of $500 per month but had not paid that obligation for a year. That would mean that you are in arrears in the payment of child support in the amount of $6,000.
But now you are the primary custodial parent. This means, among other things, that the other parent now must pay child support to you each month. Let’s assume that because the other parent makes less money than you do that the other parent’s child support obligation to you is $300 per month. But does the fact that the other parent now has a monthly obligation to pay you child support (in this case, $300 per month) mean that the child support you owed the other parent for the past year and the amount of $6,000 magically disappears as a financial obligation to the other parent? No. You still owe the other parents $6,000. How this gets paid off can be handled in various ways.
The most practical way to resolve the issue would be, in my opinion, in most cases, to apply an offset to what the other parent owes you each month ($300) against the $6,000 that you owe the other parent. that offset could be applied by relieving the other parent of having to pay you child support for a period of 20 months because $300 per month Multiplied by 20 months equals $6,000.
But that’s not the only way the court could handle this. It’s possible that the court could order the other parent to pay you $300 per month in child support and for you to pay the other parent $500 per until the $6000 arrearage is paid. Or the court might give credit to the other parent for $300 per month while you pay the other parent $200 per month until your $6,000 arrearages are paid in full, which would result in your really just being paid off 30 months instead of 20.
No matter how you slice it, however, the fact that the physical custody award switched from the other parent to you, your child support payment arrearages will not be discharged and wiped out as a result.
Utah Family Law, LC | divorceutah.com | 801-466-9277