April

I'm not UK tax resident until tax year 23/24. Every December since 2017, some of RSU shares, in US, was vested. Combined I received 3,000 shares. I sold 2,000 shares before becoming UK resident, and sold the rest 1,000 shares during tax year 23/24. Now I'm trying to calculate the capital gain tax. My understanding is that the cost for RSU = the vested price. Since I have 7 vested price (every December since 2017) does the the cost for my rest 1,000 shares to be on "first-in-first-out" (so cost = the vested price of the most recent vested 1,000 shares)?