Once again, those dates are when the forms will be ready to print for filing, or ready to e-file, just like it says at the top of that page. Those are NOT the date when the forms will be in the program itself good enough for estimations. For example, Form 1040 shows available to print December 17, but that form is in the product as released early November.
I've been doing December estimates for more than 30 years and I've never seen TurboTax not have almost all forms in the product at release time. Not for filing, not final, not bugfree, but there good enough to do estimations.
This lack of being ready for doing end-of-year tax estimates is new. Indeed, Intuit promotes TurboTax as being "Up-to-date on the latest tax laws so you have the latest information" when they are selling you the product in November, and it clearly is not.
