A message posted last night on the Intuit website acknowledged the problem. "Intuit is working with the IRS and has notified them that throughput on our electronic filing system was not what we expected, resulting in a system slowdown. We encourage customers to continue trying to e-file as we continue to work on the issue."

TurboTax users flooded the company's support forums with messages about not being able to file their returns electronically. "My returns did not transmit successfully. I was told to try again. I did for four hours. Never got them through," said user DC-Taxpayer at midmorning yesterday.

Early today, Intuit updated a running message on its site that said it was clearing the backlog. "Outstanding issues with our servers have been resolved, and we are currently processing all customers' returns and requests for status checks at a normal rate," the statement read.

"We're still digging for the root cause, but clearly, volume was a huge factor," Julie Miller, an Intuit spokeswoman, said this morning. "It was at least [two times the volume of] last year's [filing date], and even our best planning couldn't anticipate that."

Miller said that Intuit's back-end systems—those that process returns and then electronically file them—were clearing the queue "at a brisk clip." She also encouraged users who had not been able to file last night to do so today. The IRS was also going to cut Intuit customers some slack, Miller said. "We're expecting the IRS to issue a statement momentarily that will give our customers a grace period to file," she said.

Intuit's fumble has made some users swear off e-filing in general and the company's products specifically. "Never again with TurboTax unless there is a full refund and the IRS accepts the return on time," promised orbiter just before midnight Tuesday. "One thing's for sure: I will not be E-filing for another 10 years, not with TurboTax or any other software or E-file service," said another user, identified as mattP.

Miller declined to go into specifics about how Intuit will reach out to affected customers. "We're going to get through the next couple of days, and then we will talk about how to reach out to impacted customers. We know that they are extremely frustrated and anxious. This is not the customer experience people come to Intuit for," Miller said.