It is buried in various Tax updates, your accountant should be able to find it, but the goal posts are moving all the time, see below. But the main point is if you are employed and spread bet for fun then you are OK, but if it is your main source of income you may not be depending on who you talk to.
HMRC internal manual
Business Income Manual
From:
HM Revenue & Customs
Published:
22 November 2013
Updated:
2 May 2019, see all updates
Meaning of trade: exceptions and alternatives: betting and gambling - spread betting
The principles of Down v Compston [1937] 21TC60 and Burdge v Pyne [1968] 45TC320 (see BIM22019) apply equally to spread betting. To be taxable, the spread betting wins must come not merely from an opportunity presented by a trade, they must arise from the carrying on of that trade. Whether or not a particular spread bet is taxable will depend on the terms of the contract and the economic substance of what is done.
HMRC internal manual
Business Income Manual
From:
HM Revenue & Customs
Published:
22 November 2013
Updated:
2 May 2019, see all updates
Meaning of trade: exceptions and alternatives: betting and gambling - spread betting
The principles of Down v Compston [1937] 21TC60 and Burdge v Pyne [1968] 45TC320 (see BIM22019) apply equally to spread betting. To be taxable, the spread betting wins must come not merely from an opportunity presented by a trade, they must arise from the carrying on of that trade. Whether or not a particular spread bet is taxable will depend on the terms of the contract and the economic substance of what is done.