I'm using TurboTax Deluxe for Windows.
I spent most of the day yesterday working on California mortgage interest adjustments. The California worksheet is terribly flawed: it fails to pull in some critical numbers from federal, and if you override the numbers, it does the calculations incorrectly. It imposes a $100,000 cap on home equity loans, misinterpreting the California rules about home acquisition debt and equity debt. There is also no adjustment for the portion of mortgage interest reported on form 8829.
I spoke with support and after checking a few things, the agent was getting lost. It's a very complex topic, so that's understandable; I needed to speak with an Intuit California specialist. However the agent did not escalate the issue, telling me that I should use overrides to fill in the correct amounts. "Do your own calculations and fill in the form yourself" is not the advice you hope to hear from a tax program vendor.
These program errors make a difference of several hundred dollars on my state taxes, yet the program acts as if everything is fine ("you shouldn't need to change these numbers"). I wonder how many hundreds of taxpayers are overpaying their California taxes because of these incorrect calculations.
