What kind of fees can you offset against capital gains? I realise trading commissions can be offset against gains, but what about other less directly associated fees, such as Freetrade Plus membership, or “exchange connection fees” which brokers like Degiro charge. Can these fees also be offset? I would guess Freetrade plus fees could probably be offset but exchange connection fees maybe not?
Your best option is to contact HMRC and/or your accountant.
My layman’s understanding is no, since platform fees don’t directly relate to specific costs of buying and selling specific assets they wouldn’t be deductible.