EIM60730 | Tax treatment of income from Government and other Public Departments: expenses deductions under Section 336 ITEPA 2003
From HM Revenue & Customs · Employment Income Manual
Civil servants are normally reimbursed for all expenses they incur necessarily in performing the duties of their employment. So they are not likely to be entitled to a deduction for expenses under section 336 ITEPA 2003, see EIM31630. If a request for a deduction is pressed you should refer it to PD (London). Do not agree any flat-rate deduction for a non-industrial Civil Servant without prior reference to PD.