TurboTax has a 100% Accurate Calculation guarantee. However, this does not cover user error in providing tax data, user omission of tax data or user answering a question incorrectly causing the tax data to be incorrect.
See this TurboTax support FAQ for the Calculation guarantee - https://ttlc.intuit.com/turbotax-support/en-us/help-article/account-management/turbotax-100-accurate...
