While the IRS began accepting 2018 income tax returns on Monday following a month-long government shutdown, many Americans are wondering if their refunds will be delayed.

On Tuesday, the IRS had 5 million pieces of unopened mail that arrived during the government shutdown, which could take a year for the agency to resolve, CBS News reported.

During the government shutdown, IRS help centers were closed, which moved taxpayers to use the postal system, according to the news outlet. This created 700,000 pieces a mail a day for the agency,which typically sees around 200,000 pieces a day, CBS News reported.

"Just because you reopen the government, doesn't mean that on Day 1 everything is normal," Jorge Castro, a former counselor to the IRS commissioner and senior counsel to the Senate Commerce Committee who is now at the law firm Miller & Chevalier told WNCT. "There's still a backlog. The IRS has not been at full capacity in its operations for over a month."

Complicating the matter is the loss of some IRS employees that quit during the shutdown and the delay in hiring temporary workers for the tax season, according to CBS News.

The big question for taxpayers is whether or not their refund will be delayed. The IRS is expected to hold income tax returns with Earned Income Tax Credit or Child Tax Credits until mid-February as it looks to thwart identity theft and fraud, CBS News reported.

Refunds are typically processed in 21 days or less in a normal tax year the IRS told CBS News. The IRS has approximately 80,000 employees. Income tax filings are due on April 15, 2019.