Cryptocurrency is considered property for federal tax purposes as reported in IRS Notice 2014-21 (PDF) . The agency said virtual currency is an ongoing focus area for IRS Criminal Investigation.

IRS Commissioner Chuck Retting warned in a prepared statement “The IRS is expanding our efforts involving virtual currency, including increased use of data analytics. We are focused on enforcing the law and helping taxpayers fully understand and meet their obligations."

The IRS started sending the educational letters to taxpayers in mid-July. There are three variations— Letter 6173, Letter 6174 or Letter 6174-A—each strives to help taxpayers understand their tax and filing obligations and correct past errors.