Please follow the directions below to create test returns, for each of you. However, make sure you prepare the state returns also so you can get a complete tax picture.
There's also a quick way to get a comparison on the federal return for a joint return prepared in the TurboTax CD/Download software. (This won't work in the online versions, as forms mode isn't supported).
- Open your return and select Forms in the top right corner of the window.
- Click Open Form and type What-If Worksheet (it may appear as What-If Wks).
- Check the MFJ vs. MFS box at the top.
- Scroll down to Balance Due (Refund) located under Line 74.
- The second column shows the federal outcome for a joint return, and the third and fourth columns, respectively, show the outcome for the taxpayer and spouse if filing separately.
- Negative numbers are refunds, positive numbers are taxes due.
However, this doesn't give you the whole picture because it doesn't account for your state taxes. For a true apples-to-apples comparison, you'll need to create test returns.