Child support is not taxable for the child or the parent receiving it, according to IRS.gov. It is also not deductible for the parent required to pay it.
Although parents cannot deduct child support from their total income to reduce their tax burdens, About.com indicates that under certain circumstances, parents have the right to claim one or more children receiving child support as dependants. Generally, the right to claim a child as a dependant belongs to the custodial parent; however, if the final decree of divorce meets certain circumstances the other parent is entitled to make the claim. In these cases, the custodial parent can't claim the child as a deduction but still doesn't pay taxes on child support.