Back Child Support

Can you go after someone for back child support?
My ex and I had a verbal agreement, while the children were staying with me, that he would pay child support at an amount less than is determined on the child support worksheet. This went on for several years and he had paid the agreed upon amount in full.
He is now reneging on other parts of our verbal agreement & I realize that I made a huge mistake in cutting him the break that I did. He is threatening to take me to court. Can I counter-sue for the back child support that I had previously verbally agreed to not ask for?

Yes, it is possible to seek retroactive child support in court. Depending on the terms of your oral contract and whether it is deemed valid, you may be able to go after the retroactive support.