Cryptocurrency and taxes – it’s complicated
If you were mining for someone else, your earnings are considered wages, subject to regular wage withholding by your employer. If you were doing it as an independent contractor,those earnings have to be considered self-employment earnings. In other words, those earnings will not be reported as capital.
So you have both the initial difficulty of determining fair market value of the virtual currency and the added complication of properly categorizing your mining activity. Note, this is assuming employees or contractors are getting paid in cryptocurrency; regular salary paid in cash and similar payments are treated under standard income tax principles.