I understand that when MFS we do not need spouse SSN and need to mail in the papers, however I wanted to know what additional documents do I need to send along and what should be the content of my cover letter explaining why I could not provide my spouse SSN?
If you do not have your spouse's SSN when filing as Married filing Separately, you must file by mail and include a note explaining why the spouse's SSN is missing. You can describe your efforts in obtaining the SSN (not in talking terms).
Thanks for replying, are personal reasons enough to explain the missing SSN..?
Do I need to send other documents to help identify him such as passport copy, etc?
Do these kind of situations pose higher chance of rejection? Or the only downside is delay?
You can just give your spouse's name in the note. Your tax return will not be rejected because of the lack of your spouse's SSN. It just cannot be e-filed.
This IRS document says, on page 3-5:
A spouse who is Married Filing Separately is not required to provide the Social Security card for the other spouse, although the return cannot be e-filed without the spouse’s Social Security number.