Do you want to claim the dependency exemption for your child on your income tax return?
You really want IRS form 8332.
Form 8332 is required by the IRS so that your spouse who has custody of the child can release the dependency exemption to you.
You are required to attach a separate form for each child. Without the form both you and your spouse could be audited by the IRS especially if you both claim the exemption for the same child (or children).
If you are in need of child support advice, contact a reliable Hinsdale family law attorney.