Crypto trades, even crypto to crypto trades, are taxable
You recognize capital gains, capital losses, or income on crypto asset when you sell, trade, or exchange crypto. You also owe tax on crypto received as income. The following are considered "taxable events":
Selling crypto for fiat
Trading crypto for crypto
Spending crypto on goods and/or services
Receiving crypto as income, i.e. through mining or airdrops, selling goods and/or services for crypto, or receiving crypto as salary
Buying crypto with fiat and transferring crypto between your own wallets and exchanges: not taxable
Buying crypto with fiat (i.e. USD) is not a taxable event. Transferring crypto between wallets and exchanges is not taxable either. So if you buy 5 BTC on Coinbase and transfer it to a hardware wallet where you only store it, there are no taxable events.
Want to learn more? Check out our getting started guide for crypto taxes.
Unrealized vs. realized taxes
It is important to keep in mind that crypto to crypto trades realize gains or losses. If you traded crypto for crypto at the height of the bull run in 2017, you likely realized large profits — but if you continued to hold through 2018, you would have lost portfolio value while still being liable for tax on the previous tax year's gain!
Be sure to understand the difference between unrealized and realized gains and losses. Consider using the Tax Loss Harvesting Dashboard in order to track your unrealized gains and losses, so you can trade intelligently knowing your potential tax liability.