EIM31707 - The general rule for employees鈥� expenses: dealing with expenses: how to resolve a dispute: years for which assessments have become final and conclusive
Where a self assessment for any year has become final, the only way that a deduction can be permitted is by a claim under Schedule 1AB TMA 1970.
This is a claim that can be made by any person who has been overcharged in an assessment. An overpayment relief claim can be made for an omission from a return, such as forgetting to include an allowable expense, but not for forgetting to include a claim in a return. SACM2005 and SACM2010 explain what 鈥渃laim鈥� means for this purpose.
Guidance on the time limit within which an error or mistake relief claim must be made, together with guidance on how to deal with a claim is at SACM12000.