My question involves child support in the State of: Kansas

I am trying to run numbers here and I am confused as to how to calculate my son that lives with me.

I was married and had a son. He is now 13. I have legal custody of him, but the mom does not pay me child support. I agreed she did not have to pay and it was filed in the court that she would not pay. So no worksheet was done.

I was remarried and have a 7yo son that lives with his mom. I pay her child support and we are going back for an increase. I did not have custody of my 13yo when it was calculated the first time.

How does that work? Since she does not pay do I get some kind of credit/deduction or does the court not recognize the expense of him?