Before 1942 alimony paid to a former spouse was not included in the spouse’s gross income. In 1942 Congress adopted the antecedent to section 71. Although an alimony recipient must recognize gross income, section 215 provides the payer with a nonitemized deduction for the payment. Therefore, the alimony tax provisions provide a congressionally approved income-splitting arrangement which can benefit the parties by shifting income from a high-bracket taxpayer to one in a lower tax bracket. The parties can divide the resulting savings between them by altering the amount paid to the former spouse.
Kahn, Douglas A. "Alimony Treatment for a Single Payment." Tax Notes 125, no. 11 (2009): 1211-5.