The best and most accurate way to find out if you should file jointly or
separately with your spouse is to prepare the tax return both ways. To do this in TurboTax Online you will
want to create separate accounts and returns to see the most beneficial
(jointly, separate spouse 1, separate spouse 2).
OR
For a faster method, you can compare
filing jointly vs. separately with TurboTax's free calculator TaxCaster. It will give you the estimated tax
differences when filing either way. It’s up-to-date with the latest tax
laws and can estimate your 2018 taxes as well.
See this FAQ for more details on filing
separately vs jointly:
https://ttlc.intuit.com/replies/3288477