What do I enter for SSN of spouse? I'm filing married filing separately because my divorce is still pending. I don't have my ex-wife's SSN.

[xmasbaby0]

Have you filed joint returns in the past?  If so you can get her SSN from a past year tax return or from a transcript of a past return.

You can get a free transcript from the IRS or for a fee of $30, an actual copy of your tax return.

https://www.irs.gov/individuals/get-transcript

https://www.irs.gov/pub/irs-pdf/f4506.pdf

Or you can file by mail and write on the top of the Form 1040 that your spouse's SSN is not available.

The thing about filing MFS is that you both have to file the same way.   You both have to itemize or you both have to use standard deduction.   Perhaps your divorce attorney can help you with getting the information you need.

[mezo_khaled7]

We filed jointly for the year 2023, and separately for year 2024. Im going to try to get a copy of 2023 from the IRS website. Thank you for the advice! Will report back.