According to this video,
https://www.facebook.com/cnbccrypto/videos/1688689147880991/Bitcoin is considered as property and therefore whenever you sell your BTCto cash, there are two transactions. You first sell the property to cash value then what you gain from the sale is used as cash. These transactions are therefore taxable.
For HODLers, if you cash out it in less than a year then it would be considered as income so theres tax for that. If you hodl for more than a year, then IRS will consider it as 20% capital gains.
In General, taxes vary from country to country. For example, in Russia there is very little tax to work with cryptocurrency.