asked Her Majesty's Government:

Whether they will publish the calculations by which the Chancellor of the Exchequer, in his Statement on 24 January, estimated that his capital gains tax proposal would cost around £200 million a year. [HL1645]

The costs of changes to the capital gains tax regime are estimated on the basis of self-assessment data from previous years, detailed gains computations submitted with self-assessment returns and standard assumptions about macroeconomic indicators. Estimates also take account of likely changes to taxpayer behaviour and are subject to a degree of uncertainty. The Exchequer impact of the proposal will be scored in the usual way at the Budget.