Corporation tax: Profits or losses on currency exchange movements including virtual currencies are taxable. The profits and losses of a company that engages in cryptocurrency transactions would be recognized in the books and taxable under standard corporation tax regulations.
The spread is the difference between the buy and sell prices quoted for a cryptocurrency. Like many financial markets, when you open a position on a cryptocurrency market, you’ll be presented with two prices. If you want to open a long position, you trade at the buy price, which is slightly above the market price. If you want to open a short position, you trade at the sell price – slightly below the market price.

"Nevertheless, with central banks likely to begin raising rates and tapering its stimulus package, investors are looking for a store of value that is perhaps less susceptible to these changes.
The risks of loss from investing in CFDs can be substantial and the value of your investments may fluctuate. CFDs are complex instruments and come with a high risk of losing money rapidly due to leverage. You should consider whether you understand how this product works, and whether you can afford to take the high risk of losing your money.