The government shutdown won't stop the Internal Revenue Service when it comes to taxes—at least for those who filed six month extensions.
Despite the shutdown, now in its third week, the IRS is holding firm to Tuesday's deadline for filing federal forms for those who asked for and got the extension. That's some 12 million people, according to the tax collecting agency.
That has some taxpayers worried, said Scott Berger, a CPA with Kaufman, Rossin.
"Many of our clients are wealthier clients, and they estimated their returns and taxes owed for the year, and not being able to contact the IRS during the shutdown with the extension deadline, it's reason for some angst and stress," he said.
An extension of time to file is not an extension of time to pay. Tax payments for the year 2012 were still due on April 15, 2013, and many taxpayers who filed an extension paid some taxes but could owe more.
"A major problem is having all income reported as some of it, like from hedge fund investing. The information comes in late in the year, which is a reason for extensions," Berger said. "Without the ability to talk to the IRS, it's possible taxpayers could owe more in taxes."
(Read more: House GOP pushing separate bill to end shutdown)
Another shutdown related problem, said Berger, is the fact that the IRS can't review and verify powers of attorney on returns. That's when someone other than the taxpayer themselves does the return.
"They're not doing the work and this is slowing down the process," Berger said.