WASHINGTON, April 13 (Reuters) - The U.S. Internal Revenue Service needs more and consistent funding to help close a “tax gap” that is leaving perhaps more than $1 trillion in legally owed taxes uncollected every year, IRS Commissioner Charles Rettig said on Tuesday. Rettig told the Senate Finance Committee that new sources of wealth have arisen since 2011-2013, when the last official annual tax gap estimate of $441 billion was made, including cryptocurrencies and the rising use of complex, foreign-source income. “If you add those in, I think it would not be outlandish, that the actual tax cap could approach, and possibly exceed $1 trillion” on an annual basis, Rettig said. (Reporting by David Lawder)