This is getting confusing.... My job is a Chartered Accountant dealing with people's personal tax affairs, so....
The first point is that refereeing income is treated as a "self-employment", not an employment. So, the test whether an expense is allowable is "wholly and necessarily". For employment income deductions, you have to add "exclusively" in as well. Gym membership would fail under this test.
So, RA membership is allowable under these rules. Also, any mileage for refereeing matters - to an RA meeting, training evening, etc is eligible. You should be also able to claim a % of your mobile phone bill (based on usage), as it is partly used for refereeing
And for more allowable costs, you could claim for going to watch at match at your level or just above as a learning experience...
HMRC enquires into your refereeing income are very rare, as they have better recovery jobs to investigate.
