Different states have different rules regarding when a parent's child support obligation ends. In some states, a parent's child support obligation ends when a child turns 18 years old. In Massachusetts, a parent's child support obligation generally lasts at least until the child reaches age 18, but could continue until when the child turns 21 if the child is living with a parent and dependent upon that parent, or up until the child turns 23 if the child principally lives with a parent and is dependent upon that parent due to the child's enrollment in an educational program (excluding educational costs beyond an undergraduate degree). See M.G.L. ch. 208, §28.