EIM31705 - »Ê¹ÚÌåÓýapp general rule for employees: expenses: dealing with expenses: how to resolve a dispute
A request for a deduction is not a claim to a relief. So a dispute about a deduction cannot be resolved by the machinery for making and determining claims in sections 42 and 43 TMA 1970.
»Ê¹ÚÌåÓýapp mechanism for permitting relief for an expense is to deduct it from earnings to arrive at the amount of an assessment or self-assessment. So, the machinery for resolving disputes lies in an assessment and an appeal against that assessment, see EIM31706. Many disputes can be resolved without the use of formal machinery, see EIM31710.