Short version:
The exact details vary depending on whether it's an ISO or a nonqualified option, but the latter are more common. It goes like this: When you buy a stock or option from your employer at less than face value, the difference between fair market value on that date, and the amount you paid is added to your W2. Your basis, then, is the sum of what you paid and what was added to your W2. The addition may be on the W2, or not. In this case, that's your code V. Often the stock or option is sold immediately upon purchase, and the profit is exactly the same amount as was added to the W2, give or take a broker's commission and a few cents one way or the other. So, to fix the tax return, you need to go back to your Sch D, and add the code V amount to the basis...it should come out right. If you still have significant gain or loss, then study the rest of the paperwork carefully. There should be a pile of computer printouts "explaining" this. If it's an ISO, you can have gain or loss, otherwise I'd look very carefully at numbers greater than $20 or so.
Julie