I cannot give the hon. Gentleman numbers, but I can say that there have been large companies whose tax computations are calculated incorrectly each year, due to known problems in the accounting system. One group of companies had system problems every year. They could not identify the source of the problem or satisfy HMRC that the tax computation was correct. The measure is intended to encompass the small minority of large companies that do not have those systems in place. For those companies, it is difficult for either the company or HMRC to know whether the right amount of tax is being paid.