Some joint filers wonder if they would get more money back by filing separately. The only way to know for sure is to create test returns, one for each spouse, and compare the bottom lines. Be sure to also prepare the state return 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
- Click Open Form, type What-If Worksheet (it may appear as What-If Wks), and select Open Form
- Check the MFJ vs. MFS box at the top
- Scroll down to Balance Due (Refund) located under Line 72
- 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.