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HMRC internal manual

Self Assessment Claims Manual

Making and Amending Claims: Quantification by the Taxpayer

Section 42(1A) says that a claim for relief, an allowance or a repayment of tax must be quantified when it is made. We take this to mean the customer must make the quantification with a reasonable degree of accuracy.

A claim that is in a set amount, such as a claim to a personal allowance, is already quantified and so the taxpayer does not need to do anything to satisfy this requirement.