Whatever amount is reported on a Form 1099-R sent to you is income that is includible on your income tax return. For income tax purposes, you cannot split the Form 1099-R to reduce the amount that is reported on line 4 of your Form 1040.
Separately, if you pay alimony to your ex-spouse (the amount of which is determined by your divorce or separation instrument), whether or not the alimony is deductible on your tax return and includible as income on your ex-spouse's tax return depends on when the divorce or separation instrument was executed or last modified. If the amount of alimony you pay your ex-spouse includes some in proportion to the amount on amount on the Form 1099-R, if the date that the divorce or separation instrument was executed was after December 31, 2018, the alimony is neither deductible by you or includible as income by your ex-spouse. The same applies if the divorce or separation instrument executed by December 31, 2018 but was modified after that date and specifies that this same repeal of the alimony deduction applies.
