Your post was cut off in mid-sentence. What is the rest of your question? And we need more information in order to give any help. Is your ex the children's bio-father or step-father? Or is he just your ex BF who is not related to the children? Please explain. And were you the custodial parent? Who did the children live with? Did you have income from working? Did you get a letter from the IRS? Is there a letter number or CP number on the letter? What exactly does the letter say that the IRS wants from you? (Please no personal information).