The IRS is still too slow to process amended tax returns, answer taxpayer phone calls and resolve identity theft cases, according to an independent watchdog within the agency. The organization sent a report to Congress Wednesday that says while there is “cautious optimism” for the agency, the backlog of unprocessed amended returns has quadrupled from 500,000 in 2019 to 1.9 million in October last year. And taxpayer correspondence and related cases more than doubled over the same period, from 1.9 million to 4.3 million. The report comes shortly after the IRS announced that the 2024 filing season begins on Jan. 29.