TurboTax Online is not suitable for trying out different scenarios. The CD or download TurboTax software has features to accomplish what you want to do.
In TurboTax Online there is only one copy of your tax return, and any change you make is saved immediately. There is no back-out or undo, and no way to exit without saving the changes. If you want to use TurboTax Online to try out different scenarios, you could use a different user ID than the one you use for your actual tax return, but you would have to do a complete new return from scratch. If you do this, be careful to keep track of your different user IDs and passwords.
With the CD or download TurboTax software there are two ways to try out different scenarios. You can save a copy of your tax return with a different file name, then try out the changes in the copy without affecting your actual tax return. You can also use the What-If Worksheet in forms mode, which lets you try out different scenarios without changing the return at all.
Another way to try out different scenarios is to use the online TaxCaster tool, which you can access at the following link.
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/
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