Child support is payable for all children living in Australia whose parents have separated. If a child turns 18 during their last year at school then that child is eligible for child support until they complete the school year. A child who is married or living in a de facto relationship is not eligible for child support.
Usually child support requires both parents to be living in Australia, but there are arrangements with some other countries for collection and payment of child support, if one of the parents or the child is living in that country.
