The "wholly and exclusively" test is four words. Applying it to a musician's real costs is where most of the judgement happens.
HMRC's test for deductibility is deceptively simple: a cost is allowable only if it is incurred wholly and exclusively for the purpose of the trade. The obvious cases, a guitar used only for gigs, a train ticket to a session, agent commission on a live fee, satisfy the test without argument.
The hard cases are the rest. Stage clothing. A home recording studio. A meal on the road. Equipment that serves both the music business and the household. The line is not arbitrary. HMRC has litigated these questions for decades, and the pattern in the cases is consistent, but it requires judgement, not just rule-following.
This episode works through the five categories that cause most friction in practice, and gives you the analytical frame to reach a defensible position.