Example of CGT in practice:
Your taxable income (your income minus your personal allowance and any income tax reliefs) is £20,000. You sell shares that you inherited from your aunt for £35,000. When you inherited them, they were worth just £14,000. So you have a total gain of £21,000.
In calculating how much you owe, you first need to deduct the tax-free allowance from your gain. £21,000 less £6,000 leaves you with £15,000 of additional taxable income.
You need to add this to your taxable income, which leaves you with £35,000. This doesn’t push you into the higher rate tax bracket because it all falls within the basic rate band (£50,270 for 23/24). So you’ll pay 10% on the whole gain, leaving you with a bill of £870.