If you’re a Company investing in Bitcoins or other cryptocurrencies, you should treat the investment like a foreign currency. When you buy them, you should note the sterling value and, at your business year end, convert the value back into sterling. If the value has gone up against sterling, then you have what is called other operating income, and you will pay Corporation Tax on it. If you made a gain on trading, then there may Capital Gains tax to pay. As an individual you will also pay Capital Gains if you make a profit.