It is unclear from the question whether the amendment was approved by the court, the nature of the payments you owed to him under the divorce agreement or if there is a current court case pending. Depending on the terms of the 2012 amendment, you may be able to argue that the amendment acts as a waiver or at least put the burden on your ex to prove there is still money owed. Best wishes.
Answered on Jan 08th, 2015 at 2:16 PM