Beginning January 1, 2019, alimony will no longer be a tax deduction. Likewise, recipients of those payments will no longer pay income tax on alimony received. The charges are part of the larger Tax Cuts and Jobs Act of 2017.
The change is intended to increase tax revenue for the IRS since the payor of alimony is generally taxed at a higher rate than the recipient of alimony. By keeping the income on the return of the payor, the income is taxed at a higher tax rate than it would be on the tax return of the recipient.
Since 1954, gross income has included amounts received as alimony or separate maintenance payments. There was allowed as a tax deduction an amount equal to the alimony or separate maintenance payments paid. Essentially, alimony was taxable income for the recipient and deductible to the payor.
If you have entered or will enter into a divorce agreement prior to January 1, 2019, the change won't impact you. The alimony deduction repeal grandfathers in any taxpayers paying or receiving alimony under the old rule.