The head of the IRS believes more rigorous disclosures from the nation’s banks could help fix a yawning tax gap and recoup billions in owed revenues. In a letter viewed by CNBC, IRS Commissioner Charles Rettig told Sen. Elizabeth Warren, D-Mass., that relying on banks to report basic information about their customers’ deposits and withdrawals could put a big dent in annual tax evasion. A source provided CNBC access to the letter, which is expected to be released Thursday. The source disclosed its contents on condition of anonymity. The IRS chief told Warren in Friday’s letter that years of budget cuts have left the ... (full story)