The IRS is giving all taxpayers an extra day to file after its website went down on deadline day.
The agency announced that individuals and businesses with a filing or payment that was due Tuesday now have until midnight Wednesday.
It said no additional paperwork is needed to get the extension.
The agency's website for making payments and gaining access to other key services crashed amid the filing flood. The website appeared to be back to normal late Tuesday.
The IRS had earlier said it still expects Americans to pay their taxes, and U.S. Treasury Secretary Steve Mnuchin said extensions would be granted to those impacted when the site was up again. But it later extended that extension to all filers.
The IRS said in a statement that "certain IRS systems are experiencing technical difficulties." It also said that the problem appeared to be a hardware issue.
Electronic filing is the most popular way to file.
Pages on the IRS website used to view account information, make a direct payment or set up a payment plan were all not functioning most of the day Tuesday.
It's unclear when and why the failure occurred. But it appears, based on a message on the site, that the online payment system became unavailable at 2:50 A.M. ET that morning.
It's unclear how many people were impacted Tuesday but, by comparison, about 5 million tax returns were filed on the final day of last year's tax season.
The IRS snafu also caused problems for popular third-party tax preparers such as Turbo Tax and H&R Block. Both had said that they would hold onto customer tax returns and file them as soon as the IRS system reopens.
Tax day had fallen on April 17 this year because April 15 was a Sunday and April 16 was Emancipation Day, a holiday in Washington, D.C.
IRS Acting Commissioner David Kautter testified during a House Oversight Hearing Tuesday that a number of systems were down and that the agency is working to resolve the issue.
Trump's top economic adviser Larry Kudlow offered a deadpan reaction when asked about the failure.
"The IRS is crashing? Sounds horrible. Really bad," he said during a briefing with reporters in West Palm Beach, Florida. "I hope it gets fixed."
The IRS typically recommends that taxpayers use electronic filing to avoid common mistakes. Online filing is quicker than dropping something in the mail — when the site works, of course.
Jill Colvin in West Palm Beach, Florida and Holly Ramer in Concord, New Hampshire, contributed to this report.
This story has been updated.