You cannot claim a deduction for alimony paid without the recipient's Social Security number.
This is not a new requirement. What did you do in past years? If you are only recently divorced, you cannot claim the deduction at all. You cannot deduct alimony paid if you were divorced in 2019 or later.
If you claimed the deduction in previous years, the recipient's SSN should be on your tax returns for the previous years. If you are eligible to claim the deduction but somehow do not have the recipient's SSN, contact the recipient and ask for it, or ask your divorce lawyer for help getting the SSN.
