Alimony or spousal support payments are tax deductible by the payer and taxable income to the supported spouse. Child support payments, on the other hand, are typically not deductible from the income of the payer and are not included as taxable income to the supported spouse.
According to the Federal Internal Revenue Code, ". any payment which the terms of the divorce or separation instrument fix (in terms of an amount of money or a part of the payment) as a sum which is payable for the support of children of the payer spouse" is not considered alimony or a separate maintenance payment. Thus, such payments are a tax neutral event (they are non-taxable to the person receiving them and non-deductible to the person making them).
"A payment is fixed as payable for the support of a child of the payer spouse if the divorce or separation instrument specifically designates some sum or portion (which sum or portion may fluctuate) as
payable for the support of a child of the payer spouse. A payment will be treated as fixed. if the payment is reduced (a) on the happening of a contingency relating to a child of the payer, or (b) at a time which can clearly be associated with such contingency. For this purpose, a contingency relates to a child of the payer if it depends on any event relating to that child, regardless of whether such event is certain or likely to occur. Events that relate to a child of the payer include the following: the child's attaining a specified age or income level, dying, marrying, leaving school, leaving the spouse's household, or gaining employment."
Thus, under Federal income tax law, regardless of the label that is used, most child support payments are a tax neutral event, while most support payments provided to the other (former) spouse are deductible to the payer and included in the taxable income of the supported spouse.