What is the primary benefit of using the "What-If" analysis tool in TurboTax?

The primary benefit of using the "What-If" analysis tool in TurboTax is that it allows users to see how different tax scenarios can affect their tax liability. This feature is particularly valuable for individuals who are considering various tax strategies or life events that might alter their tax situation, such as changes in income, filing status, or deductions. By inputting different hypothetical scenarios, users can visualize potential changes in their tax outcomes, which helps them make informed financial decisions throughout the year.

While other options provide useful information regarding tax processes, they do not offer the interactive, predictive capabilities that the "What-If" analysis tool provides. The historical overview of past tax returns serves as a record rather than a predictive tool. Calculating potential penalties is specific to certain situations and does not encompass the broader analytical capabilities of the "What-If" feature. Similarly, generating a summary of available deductions helps in tax preparation, but it does not allow the user to explore the implications of making different choices regarding those deductions or other factors. Thus, option C stands out for its proactive and exploratory approach to understanding tax implications.