This article will show you how to enter child support payments made by the taxpayer on a 1040 return.
According to IRS Publication 504, child support payments are neither deductible by the payer, nor taxable to the payee:
"A payment that is specifically designated as child support under your divorce or separation instrument is not alimony. The amount of child support may vary over time. Child support payments are not deductible by the payer and are not taxable to the payee."
Refer to IRS Pub. 504 for more information.