Bitcoin and CryptoCurrencies as a Legal Taxable Asset

In some parts of the world though they are treated as legal tender, so it really depends on the environment where transactions are taking place. More info on this for IRS tax purposes can be seen here: https://www.irs.gov/pub/irs-drop/n-14-21.pdf.

At the very least, bitcoin/cryptocurrencies are comparable to stocks and commodities, both of which fluctuate in price. In that case, capital gains need to be reported.