The Internal Revenue Service building in Washington. (Susan Walsh/ AP)

Microsoft on Tuesday stopped providing free support and security updates for Windows XP. The long-planned expiration of the popular operating systems has sent millions of users scrambling to upgrade their computer systems.

Among who still that need to make the transition is the Internal Revenue Service, which has yet to complete its migration away from Windows XP, less than a week ahead of its own important deadline: Tax Day.

The agency is "struggling" to find $30 million dollars to complete its move to Windows 7, according to Rep. Ander Crenshaw (R. - Fla.), chairman of the financial services and general government subcommittee. During a hearing on IRS budget Monday, Crenshaw questioned why the agency had not prioritized the move "even though Microsoft announced in 2008 that it would stop supporting Windows XP past 2014."

IRS Commissioner John Koskinen defended the agency's efforts, noting that it has been operating amid budget uncertainty for years. The migration to Windows 7 was just one of nearly $300 million dollars worth of information technology projects that has not been completed due to funding shortfalls, he said.

"You're exactly right," Koskinen said of the timing.  "It's been some time where people knew Windows XP was going to disappear." But testifying just a day before Microsoft ended support for the operating system, he conceded the agency was still trying to finish up the transition.

"So we are very concerned that if we don't complete that work, we're going to have an unstable environment in terms -- in terms of security."

In a statement to The Washington Post, the IRS confirmed that it was still in the process of transitioning the laptops and desktops at the agency from Windows XP to Windows 7.

But don't worry, this won't affect IRS's ability to process your tax returns. The agency insisted that the lag would have no impact on taxpayers, saying "none of our filing season systems or other major business operating systems for taxpayers use Windows XP. "

To date, the IRS says it has upgraded more than 52,000 of its 110,000 workstations to Windows 7 and is working to complete updates by the end of the year.

In the meantime, the IRS has signed an "extended support" agreement with Microsoft that will provide access security updates across the agency for a year. "We are taking appropriate steps to ensure our networks, systems and taxpayer data are safe and secure," the statement said.

And the IRS is likely not alone in migration limbo.

In March, The Post's Ellen Nakashima and Craig Timberg reported that about 10 percent of government computers would continue using XP as of Microsoft's end of support deadline. The figure includes thousands of machines on military and diplomatic networks used to secure classified information.

The United States isn't the only government in this predicament. Some other countries, including Britain and the Netherlands are also paying millions of dollars to set up extended support contracts with Microsoft to keep their systems serviced while they transition away from Windows XP.

Read more:

Windows XP support ends today. But it’s still used everywhere from governments to ATMs.

Mourning the end of XP? We’ll help get you through it.

Government computers running Windows XP will be vulnerable to hackers after April 8