A bipartisan group of 100 members of Congress is pushing the IRS to address numerous concerns, including a massive backlog, ahead of the April 18 filing deadline for taxpayers.

Democratic U.S. Rep. Abigail Spanberger of Virginia, along with Sens. Bob Menendez, D-N.J., and Bill Cassidy, R-La., spearheaded a letter sent to IRS Commissioner Charles Rettig to make clear “that the agency’s lack of action is causing unnecessary confusion, as the current 2022 tax filing season is underway.”

Among the issues lawmakers want the IRS to address is “which notices are statutorily required to be issued within a specific time, and why there are still certain notices that have not yet been suspended,” according to a news release issued by Spanberger’s office Monday.

The IRS sends notices, or letters, to taxpayers for various reasons, such as issues with federal tax returns or payment requests.

Last month, Spanberger and Menendez led a bicameral effort with 45 colleagues urging the IRS to take immediate steps to reduce its massive backlog and improve its customer service.

On March 10, the IRS said it plans to hire 10,000 new workers to chip away at that backlog, which totals around 20 million pieces of correspondence, including unprocessed returns. That is more than 15 times as large as in a normal filing season, according to the agency.

Despite an increasingly complex tax code and population growth, the IRS workforce has not increased since 1970. The slew of pandemic-related aid programs that the agency had to administer further added to the strains.

But many Republicans over the years have pushed back on calls to boost funding, or cut funding, that would have helped the IRS increase staffing and modernize its aging systems.

The recent $1.5 trillion omnibus federal spending package passed last week would provide $12.6 billion to the IRS, the largest funding increase for the agency since 2001.

The Associated Press contributed to this report.