Married Filing Separately - No Spouse SSN

No way for her to get copy of prior year from the preparer?

I can't imagine not knowing your spouse's SS#.  

Will it efile if you disable error checking ? 

I’m going to go with paper if you can’t twist someone’s arm to get the Social Security number 

Contact his attorney to speak to her attorney to get the required SSN.  It'll only cost $3,000 of lawyers fees but you'll have your answer.  What able adult does not know their own Social Security Number or have it on some piece of documentation somewhere?  I think we know why they're filing married-separate.

this is why i try to avoid mfs - spiteful problematic. remember: you have right to refuse service to anyone.

I always dig into "who has the paperwork" such as old W2 and paystubs, checking account and credit applications, medical coverage, any online account where you can see who is authorized or a beneficiary, even a mortgage or car loan. Anything that would be reported to a credit agency will have full SSN. I love it when someone separates, but isn't bothered digging out their part of the legal paperwork that was part of that "family."

She can get a copy at IRS.gov if she registers an account