The IRS considers cryptocurrency as property, which is held for investment purposes. This means that if you are holding or trading cryptocurrency on behalf of someone else, then you’re probably subject to capital gains tax. If this is the case, then your employer needs to issue Form 1099-B “ Proceeds from Broker and Barter Exchange Transactions” in order for you to be taxed on the income.
On the flip side, if you are holding crypto yourself (i.e., buying/selling for profit), then you will be taxed on whatever profits your activities make over time. There are many nuances here; consult with a professional who can help walk through all of them with you!