The fact that you can buy the 2021 program before it is ready is because users demand the early program and the DIY companies are happy to lock you into their program even though it is not a fully functional program yet ... this happens every year and the program will be updated to the new tax year eventually.
If you want to use the program for estimations then you should be using the fully functional 2020 downloaded version in the forms mode using the What If tool.
When will my forms be ready?
Historically, IRS tax forms start becoming available in January, with a few stragglers (most notably Form 1040X) getting finalized in February.
State tax forms can become available for filing any time between December and late February, depending on the state and the tax form.
For specific forms and dates, refer to the Forms Availability Table for your TurboTax product, see the related information below.
Can I Still Work On My Return Before My Forms are Ready?
Yes, according to the following:
Federal Taxes
You can still work on your return and finish most of it. Once your forms become available, we’ll create the forms and include all of your info.
You’ll only be able to e-file or print your return once the forms are available.
While you’re working on your return, we’ll ask if you want to receive email updates when your forms become available.
State Taxes
If your forms aren’t available, you’ll get a message asking you to return once they become available.
While you’re working on your return, you’ll have a chance to let us know you want to receive email updates when your forms become available.
