Yes, you may need to pay tax on cryptocurrency in the UK. HM Revenue and Customs (HMRC) treats cryptocurrency as a type of property for tax purposes, so any gains you make from buying and selling cryptocurrency may be subject to Capital Gains Tax.

The amount of tax you'll need to pay will depend on several factors, such as the amount of profit you make, your tax bracket, and any other income you have. If you're unsure about how to calculate your tax liability on cryptocurrency, you may want to consult with a tax professional.

It's worth noting that HMRC has cracked down on cryptocurrency tax evasion in recent years, and has taken steps to ensure that people are paying the right amount of tax on their cryptocurrency transactions. If you're buying and selling cryptocurrency, it's important to keep accurate records of all your transactions and to report any gains or losses on your tax return.