Whether you have to pay taxes on cryptocurrency, differs per country, but in most countries you do. In the USA cryptocurrencies are treated as ‘capital gains’ (like gold), and not a regular currency like the dollar. But trading cryptocurrency to fiat currency is a taxable event. In the UK, you usually only pay taxes on the profits that you make, but this differs based on the amount. Visit the official website of your national tax service or give them a call to find out what your situation is.
Chances are you’ll have to report your cryptocurrency and pay some amount of taxes on it. It’s advisable to do this as stated by the law. If you fail to report it, make a large profit, and then transfer your cryptocurrency to fiat money, it’s likely the tax administration will ask you where your money came from.