EIM36530 - Deductions from earnings: capital allowances: meaning of "machinery or plant"
There is no statutory definition of what constitutes 鈥減lant鈥�. Broadly speaking, to qualify as 鈥減lant鈥� an item must have a working life of at least two years (see CA21100).
If an item does not qualify as plant or machinery you will need to consider whether a deduction is due under the general rule for employees鈥� expenses in Section 336 ITEPA 2003 (see EIM31600 onwards and EIM36510).