Hi,
Your gain is usually the difference between what you paid for your asset and what you sold it for. There are some situations where you use the market value instead.
Capital Gains Tax: what you pay it on, rates and allowances
Inheritance Tax is only due when a person's estate is worth over £325,000 when they die, or if the person who died gave away more than £325,000 in gifts in the 7 years before they died. In this scenario the person in receipt of the gift within those 7 years will be liable to pay inheritance tax.
Gifts made in the last 7 years use up the £325,000 tax free allowance first, but if the gifts received are less than the £325,000 inheritance tax free allowance, any unused threshold can then be used by the estate of the person who has died.
If the person who died owned their home (or a share in it) the tax free threshold could be increased to £500,000.
You can find out more information here:
Work out Inheritance Tax due on gifts
Thank you.