No, that's not the way to do it.
The what-if (worksheet) feature works on a Married Filing Jointly return. You have to enter both your information into one tax return. Afterwards, you'll find the What-if worksheet and indicate, at the top of the form, that you want to compare MFJ versus MFS. Scroll down and view the results.
- 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.
