Where you live changes the income tax on your RSUs, but not everything. Scotland sets its own income tax bands and rates for earned income, which includes RSU vests. National Insurance and Capital Gains Tax are reserved to the UK and do not change.
What rate will my vest be taxed at?
Scotland has six bands. A vest stacks on top of your salary, so it is taxed at your highest Scottish rate. For higher earners that is the 42% higher rate, the 45% advanced rate, or the 48% top rate above £125,140.
Does the £100,000 trap still apply in Scotland?
Yes. The personal allowance is a UK-wide rule and tapers away between £100,000 and £125,140 wherever you live. Combined with Scottish rates, the effective rate on a vest in that band is even higher than in the rest of the UK.
What about selling the shares?
Capital Gains Tax on a later sale uses the UK rates and the UK £3,000 allowance, regardless of Scottish residency. Only the income tax at vest follows the Scottish bands.