When will 2018 Turbotax Home and Business be available for purchase?

Usually mid- to late November.  However, because of the tax law changes, it will probably only contain unofficial draft forms, and we have no idea when the IRS will actually approve the final forms and final software to be able to actually file.

If you need to do some 2018 tax planning you need to use the 2017 program's What-If tool ...

If you want to play around with different figures and tax scenarios without affecting your original return you can 

>>> In the TurboTax CD/Download software by creating a test copy: 

1.  Open your return in TurboTax. 

2.  From the File menu, choose Save As. 

3.  Give the copy a new name to distinguish it from the original (for example, by adding "Test" or "Example" to the file name). 

4. Click  Save. You are now safely working in the test copy and anything you do here will not affect the original. 

 https://ttlc.intuit.com/questions/1900642-how-to-make-a-test-copy-of-your-return

>>  use the WHAT IF tool: 

- Click Forms Icon (upper right of screen) or Ctrl 2 (forms view) 

- Click on the Open Form Icon 

- In the “Type a form name.” area type What-If (with the dash), click on the name of the worksheet - click on Open Form 

- You will see the worksheet on the right side of the screen; enter the information right into the form 

- To get back to interview mode - click on the Step-by-Step Icon (upper right of screen) or Ctrl 1