Jensen gave you some great info to get you started.

Typically when I see RSU vesting it will be something like 10 shares vested consisting of 4 shares withheld to cover taxes and 6 shares delivered to broker.  The 6 shares show up on the 1099-B when sold.  Some brokers don't have any information that there were 4 additional shares vested and withheld, but some do.  Income from the full 10 shares vested shows up in the W-2.  I always get the last year-end paystub and tie YTD RSU compensation to the value of the shares vested and then to the basis in the shares delivered to broker.  If you have trouble with that, there should be an exercise report / pay stub for each lot exercised / vested that breaks down the compensation, taxes, etc.  You may just need to get all of these and crunch the numbers.

Also, typically I see NQSO sales reported on a 1099-B as covered but with "bad" basis reported.  I've been told this is per IRS instructions and MOST brokers also include a supplemental schedule that shows the actual basis in the shares (including amounts reported as taxable compensation in the W-2).  So, moral of the story, don't rely on the 1099-B "reported to IRS" numbers as basis.  Do your own homework and follow the shares.

As Jensen pointed out above, it's going to be key to follow the number of shares and not just try to follow the dollars.

Rick