Deducting Alimony Payments at a Glance
You can deduct alimony paid to or for a spouse or former spouse under a divorce or separation decree, regardless of whether you itemize deductions. Voluntary payments made outside a divorce or separation decree are not deductible. If you do not enter your spouse's Social Security number (SSN) or individual taxpayer identification number (ITIN) on Form 1040, U.S. Individual Income Tax Return (PDF), your deduction may be disallowed.
Publication 17, Your Federal Income Tax - Chapter 18, Alimony - Essential guidance
Publication 504, Divorced or Separated Individuals - See Alimony for detailed guidance