That depends upon your state. You may get some ideas here.
http://www.google.com/#sclient=psy&hl=en&source=hp&q=child+support+ssi&pbx=1&oq=child+support+ssi&aq=f&aqi=g3g-v2&aql=t&gs_sm=e&gs_upl=209l900l1l4l4l0l1l1l0l324l732l0.1.1.1l3&bav=on.2,or.r_gc.r_pw.&fp=73edc9aee1714464&biw=853&bih=564
Also, do your own Google search, adding the name of your state to the search terms.
how do you file child support if the other parent is on ssi?
2 answers
Contact Social Security Office in your City... So that the child will get some of that SSI (:-)