Treasury officials say the Internal Revenue Service will face “enormous challenges” during this year’s tax filing season.

The Treasury Department reportedly warned Monday of a “frustrating season” for taxpayers and tax preparers as a result of delays caused by the pandemic, budget cuts and federal stimulus measures.

Treasury officials said during a phone call with reporters that the Internal Revenue Service will face “enormous challenges” during this year’s tax filing season, the Washington Post reported.

The Treasury Department did not immediately respond to a request for comment.

IRS officials enter filing season with an unaddressed backlog of roughly 1 million returns, but this year the IRS will enter the filing season facing “several times” that, Treasury officials said.

The IRS closed last filing season with more than 35 million unprocessed returns, a fourfold increase from the last year before the pandemic.

The pandemic forced the closure of many in-person centers where paper forms are processed, while also affecting the IRS workforce.

Budget cuts to the IRS prior to the pandemic led to a roughly 25% decline in the size of its staff. 

“By definition, no matter how much more efficient you are, you can’t lose 25% of the workforce and assume you can do the same volume of work. It’s a problem across the board — information technology; revenue agents; people answering the phones,” said John Koskinen, who served as commissioner of the IRS under presidents Barack Obama and Donald Trump.

Treasury officials said the IRS workforce is the same size it was in 1970, despite the population growing by 60%, CBS News reported.

The processing technology dates back to the 1960s and there are also fewer auditors than at any time since World War II. 

The Treasury Department said that tax filing season for 2021 tax returns will begin on Monday, January 24. Officials said there are no current plans to extend that deadline this year, urging taxpayers to file as early as possible.