Say I had 100 RSUs granted, and when vesting shares trade at $10. My employer will aim to withhold 54.59% to cover income tax/employee NIC/employer NIC.
The following day, when my employer actually sells the shares, the shares trade at $9. Given that (100 * $10 * .5459)/$9 = 60.6, my employer sells 61 shares to cover taxes. The extra .4 share proceeds, .4 * $9 = $3.6 will be refunded to me via my regular payslip.
Given the price difference between the $10 used for tax purposes, and the $9 price during the disposal, can I claim a ($10 - $9) * 61 = $61 capital gain loss? I looked up the HMRC's website but couldn't find a definitive answer.
For the purpose of this question, let's ignore the need to convert USD to GBP for tax purposes which follows it own rules and are irrelevant here.