The government is issuing a warning today for Americans to be on high alert for tax-season scams that feature fake IRS agents.

Lois Dilibero said a fake IRS agent left a voicemail on her phone recently.

"They said, 'You need to call us right away. You're being sued for $5,000 by the IRS,'" Lois Dilibero told ABC affiliate WPLG-TV in Miami. "I thought, 'Yeah, really?' … I knew I didn't owe any money to anybody."

In Dilibero's case, she said she knew immediately that it was a scam.

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Tim Camus, a top investigator with the U.S. Treasury Department, said even he got a call demanding that he pay $750 or get arrested.

Nearly 3,000 people have already fallen victim, scammed out of more than $14 million, according to the US Treasury Inspector General for Tax Administration.

And half of that money has come from these five states: California, New York, New Jersey, Florida and Pennsylvania.

The scammers, often overseas, disguise their phone numbers to make people think they're calling from the IRS and then make serious threats of jail time and even deportation.

The IRS says it would never call demanding immediate payment and would never make a person pay with prepaid cash cards or ask for credit card information.

The agency said it also would not threaten to arrest you.

ABC News' Clayton Sandell contributed to this story.