Cashing in RSU's held in US - tax treatment

[pb125770]

Hi,

So I get awarded RSU's every year by my US based employer (Restricted Stock Units). These units vest on a quarterly basis over 8 quarters. I pay withholding tax on these through the selling of a small number of shares from the portfolio each year (in the US). I'm now looking to cash in a large chunk of those RSUs' - let's say £100k for the sake of argument. I'm receiving a range of opinions from my co-workers in terms of my potential CGT liability.

My understanding is that I take the 'fair value' of the stock at the time of vest and subtract that from the value at time of selling. The difference (assuming its a gain) is my taxable amount? So for example, if I cash in £100k worth of RSU's and the fair value prices at vest totalled £25k then I have to pay CGT on the £75k gain.

Does the fact that I've been paying withholding tax over a number of years have any bearing?

Or is it more complicated than that?

Is there an efficient way to cash these in (apart from the obvious pre-post April date)?

Thanks, Paul.