Child Support - No. Child support payments are not subject to tax.

Child support payments are not taxable to the recipient (and not deductible by the payer). When you calculate your gross income to see whether you're required to file a tax return, don't include child support payments received.

Alimony - Alimony (including separation or maintenance payments) may be subject to tax depending on several factors, including the execution date of the divorce or separation instrument. In general, the term, “divorce or separation instrument” means your divorce decree, separation agreement or decree, or order of temporary maintenance. 

Except as provided below, under divorce or separation instruments executed before 2019, alimony payments are taxable to the recipient (and deductible by the payer). When you calculate your gross income to see whether you’re required to file a tax return, include these alimony payments.

However, under divorce or separation instruments executed: (1) after December 31, 2018, or (2) on or before December 31, 2018, but modified after this date, alimony payments are not taxable to the recipient (and not deductible by the payor) if the modification expressly provides that alimony payments are neither includable in, nor deductible from, income. When you calculate your gross income to see whether you’re required to file a tax return, don’t include these alimony payments.

See Publication 504, Divorced or Separated Individuals for information on what payments qualify as alimony.