"I got a single 1099-B from my employer that shows the TOTAL for ISO
stock I sold. However, I sold multiple lots acquired over several years
and they are all different sales as the basis and gain are different for
each."
Well, no. You have one sale, it just happens that that one sale comprises several lots of stock. And you certainly can tell TurboTax that you got a 1099-B and report the sale correctly.
There are several ways of attacking this. I'm assuming that these are qualified sales and/or disqualified sales where the compensation income is reported on your W-2.
Usually I don't recommend using the ISO step by step interview except in the case of stocks sold via an ISO. Ordinarily I'd say simply use the TurboTax default 1099-B input form, enter "various" in the date acquired field and then enter the correct basis sum in the cost field. (If some sales are short term and some long term then you break that sale into two parts and report each part accordingly.) But since you obviously did not sell all your ISO shares in the year you acquired them you should have used the "ISO Exercise and Hold" interview each year to report the unsold shares for purposes of AMT. That means that when you finally do sell those shares you need to report a different basis for AMT purposes than for "regular" tax, and using the ISO step by step interview makes the needed adjustment for you.
So, tell TurboTax you got a 1099-B, and tell TurboTax you'll enter one sale at a time. On the TurboTax "Tell us about your [Broker Name] 1099-B" page enter the 1099-B exactly as it reads. You can put "various" in the date of acquisition box. Then click the "Guide me step by step" blue box, tick the "I have sales from an Employee Stock Plan..." bubble and specify "ISO." You'll tell TT that you sold in 2017 shares acquired in a prior year, tell TT then total number of shares sold, and then on the page "How Did You Buy the Shares You Sold?" page tick the "At different times (multiple lots)" bubble.
The following interview will allow you to enter information on a lot-by-lot basis.
Tom Young
