When you buy Bitcoin and sell it for a profit, you are subject to capital-gains taxes. This is the case whether you buy Bitcoin and sell it for dollars or whether you exchange it for other cryptocurrency for a profit. This is also the case if you buy Bitcoin, it goes up in value and then you exchange the Bitcoin for goods or services.
The IRS has given guidance twice on cryptocurrency tax issues in IRS Revenue Ruling 2014-21 and 2019-24. The critical determination by the IRS in 2014 was that cryptocurrency is property, not currency, for federal tax purposes.
