If you filed a last-minute tax return, you may see your 2021 refund faster than you’d expect. 

Nine out of 10 refunds have arrived within 21 days this season, according to the IRS. As of April 15, the agency has issued more than 78 million refunds worth over $242 billion in total, and the average refund is currently $3,103, the agency reported.

However, there are several reasons why an e-filed return may be delayed, the IRS says. Your filing may need a manual review for missing information, mistakes or identity theft issues.

Last year, the IRS flagged millions of returns for stimulus payment errors, and the agency warned taxpayers to double-check filings.

“We urge extra attention to those who received an economic impact payment or an advance child tax credit last year,” IRS Commissioner Chuck Rettig said in a statement. “People should make sure they report the correct amount on their tax return to avoid delays.”

National Taxpayer Advocate Erin Collins stressed the agency’s challenges with paper in her annual report to Congress in January, calling it “the IRS’ Kryptonite” and pointing to a December backlog of 5 million pieces of taxpayer mail. It continues to be an issue. 

“Paper remains at the heart of the agency’s challenges in processing both tax returns and correspondence,” Collins said at a House subcommittee hearing on April 21. 

While it may take 21 days to process error-free electronic filings, refunds for paper returns may take “six months longer,” Collins estimated. 

As of April 15, the agency received nearly 118 million electronic returns — roughly 96% of filings. That may change as more returns arrive before the Oct. 17 extension deadline.

The fastest way to get an update on your refund is through the “Where’s My Refund?” online tool or by using the IRS2Go app. The portal shows three steps of the process: return receipt, refund approved and refund sent, with an estimated deposit date.

You can see the status 24 hours after the IRS receives your electronic filing or four weeks after mailing your paper return. The agency updates the portal daily, typically overnight. 

If your refund is different than expected, part of the funds may have been diverted to past-due federal or state taxes, unemployment debt, child or spousal support or other federal debt, the IRS says. 

A smaller payment may also reflect an error on your return, such as the amounts reported for your stimulus or child tax credit.