Owen, I think you are saying vesting day (i.e. when the shares show up in your account) note technially when you are given RSUs (1 year or more before they vest), in most cases the cost basis is zero, so there is no W2 impact until it Vests. and then the vest day price (average of high and low for the day) defines the amount in your W2 (or what should be in W2). And that price defines the cost basis Shares left * vest day price = cost basis. So when you sell the stock the investment income can easily be determine from that. Really the What is in the W2 is a really just a check to make sure everything is working correctly. On my paycheck (not on W2 specifically) i see the amount of income gained by RSU separately, so I can use my last paycheck to validate that the numbers are close.
