I want to change my sons last name but I don't know if that will affect his child support.

You need to legally change the child's last name through adoption. And if that is the case it will definitely affect his child support. You just can't willy nilly change a child's last name unless he is legally adopted. Does the father know about this possible name change? He may not agree to the adoption and then the child support would continue.

Well, if the non custody parent who is paying support will agree and sign for a legal name change, The court will most likely allow it. And it should not effect child support, since the person paying support agreed to the name change.

You don't need adoption, but you do need to go through the courts to change the name. And that would require the father to agree to the name change.

If the court grants the change it won't affect support. But if he doesn't agree, its unlikely the change will be allowed.

Thank you very much! You have been very helpful :)