Child Support Forms ; 4-3b. Addendum to Support Petition– Request for Child Support (IV-D) Services.If you wish to begin a new support case or reopen an old case the following documents are required to be completed and submitted to Montgomery County DRS. Use this program to ask (or "petition") the Family Court to change a support order if there is a "change in circumstances." The Montgomery County Domestic Relations Office will be located at suite 204 on the 2nd floor of One Montgomery Plaza. In order to complete this form, you will need a copy of your existing child support order. If you do not have a copy, ask the Clerk of Court how to get one. Once a child support case is filed, it takes an average of 1-2 days to be processed. You can file this petition online with the Montgomery County Domestic Relations Section (DRS) or fill out the petition and mail to: P.O. Box 311. If the other side has an attorney, mail the papers to that attorney.