Perhaps it’s not knowing the law but I’ve ran into the trend (albeit small) where the NCP continues paying the CP support while having physical custody of the child.

In a typical example case, a CP mom sends son to go live with dad and dad agrees. Dad had been paying mom regularly and therefore owes her no back child support arrears. The mutual custody swap is done and son lives with dad for 6 months. All of this is done privately outside of attorneys, court, and the AG’s child support office. There’s no paper trail to prove the swap and dad (nor mom) follows up to stop, modify, pause/abate, etc. the child support monies still coming in through garnishment.

Question: if the son returns to mom, what should happen to that money that was sent to mom while dad had the child? This question is especially important if mom and dad have a falling out. And come to think of it, who should bear the burden of having to ask the court/AG to stop the support obligation while the son temporarily lives with dad? This scenario does happen and the blowup comes when dad realizes he’s thousands in arrears from child support “debt” having accrued during the window of time he had the child; and he’s now seeking the court through an attorney or the AG to give him credit  toward the arrears he allegedly owes mom. Needless to say, in this kind of scenario, some CPs may not be so forthcoming with admitting the NCP is entitled to credit. Additionally, later if dad sues mom for relief or  mom sues dad to collect the alleged arrears, who should have the burden of proof, dad to show he never owed the money or mom to show he owed it? 
My take? Dad probably has the burden of getting the alleged arrears erased because he was ordered to pay and he, after the custody swap, could have alerted the court/AG to get the support terms changed.
The above is for informational purposes only and does not constitute legal advice nor does it create an attorney-client relationship between the writer and reader. It is prudent to speak with an attorney before making any major legal decision.
Mac Pierre-Louis, an attorney at The Law Office of Pierre-Louis & Carr, PLLC based in Houston, TX, writes about child support law issues. He is bar licensed only in the states of Texas and Florida.