The Internal Revenue Service says it expects to process the last of the 2021 returns that have been backlogged by the end of this week.

Last year was the “most challenging year ever for taxpayers” according to the National Taxpayer Advocate, an independent organization within the IRS. Issues with the pandemic and staffing shortages led to the IRS beginning 2022 with a significant backlog, which it has been working to whittle down, amid growing frustration from taxpayers.

“As of June 10, the IRS had processed more than 4.5 million of the more than 4.7 million individual paper tax returns received in 2021,” the IRS said in a statement.

As for 2022 returns, there’s some good news, but there’s still work to be done. The IRS says it has processed “the vast majority” of returns filed this year, but “more than twice as many returns await processing compared to a typical year at this point in the calendar year.”

A bright spot: A greater percentage of this year’s unprocessed returns are original returns, which, generally, take less time to process than amended returns.

“Completing the individual returns filed last year with no errors is a major milestone, but there is still work to do,” said IRS Commissioner Chuck Rettig. “We remain focused on doing everything possible to expedite processing of these tax returns, and we continue to add more people to this effort as our hiring efforts continue this summer.”

The agency renewed its call for people to e-file when possible. Returns without errors that are sent electronically largely bypass the backlog and are typically processed within 21 days.