A complex tax calculation based on the sale of an asset that has risen in value over a
number of years.
Capital gains tax (CGT) is calculated on your sale proceeds less the original cost and any additions. Your annual exemption is then taken off anything left over is taxed at 22% for basic rate tax payers and 40% for higher rate tax payers.
In practice the theory is simple but gets more complicated due to taper relief and indexation.