The reason that you are on the hook for his share of the rent is that when you signed the lease you both collectively and individually became legally responsible for it. This is known as "joint and several liability", which means that if 1 tenant doesn't pay their share of the rent then the other tenant(s) is liable for it. A landlord is entitled to be paid in full.That having been said, you can take your child's father to court and sue for any rent money that you are out-of-pocket because he afiled to pay his share. If you win, you will be awarded a judgment. Then, you could have the notation of the judgement placed on his credit report. Why don't you inform him of this and see if that prompts him to come up with some of the rent. Otherwise, you can use the judgment to garnish his wages and/or seize his other personal assets, such as a bank account.