I have RSUs that I sold last year from employer that I left in 2017 (so no '18 W2). Etrade cannot by law report the tax basis. I know the basis but not where to enter it

[DanielV01]

Enter as an adjustment.  This is how the IRS wants you to enter the trade.  First, they want you to enter the basis as they receive it ($0).  Then, you use your RSU statement (Hopefully Form 3922) to show the correct basis to the IRS through an adjustment.  This will raise the basis to report the correct amount of gain (or even loss).

This FAQ will get you back to the 1099-B screens to enter the transaction.  After you enter the main information on the first screen, select the option "I have additional information" at the bottom.  After that, scroll down to the box 2 section, and you will see an option for Corrected Cost Basis.  This is where you enter what you have been reported as your RSU cost basis.