"In 2014, the IRS issued a notice clarifying that it treats digital currencies such as Bitcoin as capital assets and are therefore subject to capital gains taxes. “The notice provides that virtual currency is treated as property for U.S. federal tax purposes,” it reads. “General tax principles that apply to property transactions apply to transactions using virtual currency.”
The character of gain or loss from the sale or exchange of virtual currency depends on whether the virtual currency is a capital asset in the hands of the taxpayer.
Thus, not every transfer of funds is considered a sale. For the user, sending bitcoins from a Coinbase account to their Trezor hardware wallet, for example, is only a transfer and not a sale since the user is still in possession of the coins.
“You should keep your own records for best results and update the report accordingly,” Coinbase support explains. “For example, if you transfer funds offsite to a desktop wallet, and then back again, you would not count this as a sale of digital currency.”
http://bitcoinist.com/irs-tax-bitcoin-coinbase/
