If you are filing as Married Filing Separately, you can leave the SSN for your spouse blank and continue with the tax return. When asked to Check this entry for the SSN, click on Continue. On the screen Run SmartCheck Again, click on Done
See this TurboTax support FAQ when your spouse is a nonresident alein - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-credits-deductions/file-taxes-spouse...
