There is no basis for that assertion at all. People will complete their self-assessment form in the way that they do now. They will state their income and the calculation will be made. There is no reason at all why this change will alter the accuracy with which people complete their forms.
There is a clear case on fairness grounds for this change, which I touched on in my earlier remarks. At the moment, a taxpayer gets relief from their personal allowance at the highest rate of tax that they pay. That means that a basic rate taxpayer gets the benefit of £1,295 and a higher-rate taxpayer gets the benefit of twice that sum, which is £2,590. It is entirely right, at a time when all of us acknowledge that fiscal consolidation is required, that people at the high end of the income range should contribute somewhat more.