Lori Whalen owed $3,845.48 in unpaid taxes and if she didn’t pay immediately, the caller warned, she could lose her Las Flores home, business and retirement savings.

A federal judge could enlarge her debt to $72,000 and require payment within a week, the caller said; her assets could be frozen, her possessions auctioned off one by one.

“We will sell everything until we can get that money,” the caller, who identified herself as IRS Officer Michelle Keith, told Whalen recently.

All lies, Whalen learned too late.

The bogus threats were part of increasingly popular scam used to cheat taxpayers across the nation. In December alone, federal consumer protection officials logged about 6,500 complaints of IRS imposters, up from just 94 such complaints in July 2013.

Whalen was skeptical initially. She hadn’t received anything in the mail from the IRS, and she demanded that “Officer Keith” provide an explanation and a badge number.

The caller supplied a badge number (282468) and three dates that she said the IRS mailed letters to Whalen. The tax agency also put a written notice on her door and verified with her neighbors that she hadn’t moved, the caller said.

“I know that you have gotten those (notices) and you have ignored them,” the caller told Whalen.

Through fear and seeds of doubt, Whalen grew convinced that she must have overlooked paying taxes on some of her work as a registered nurse. She’d never been the victim of a scam before and trusted the caller’s word.

“Once they get ahold of you, they have answers for everything,” Whalen lamented in retrospect. “I literally was held hostage for four hours until they got what they wanted.”

Authorities say Whalen’s experience can serve as a warning, and point to statistics that suggest the IRS scam is exploding in popularity just in time for this year’s tax season.

That boom raises several questions that investigators at the Federal Trade Commission can’t yet answer. Why and how the tax scam has spread so quickly, for example, isn’t known.

Last year, the IRS offered some details that it’s seen as a pattern nationally:

• “Callers are frequently insulting or hostile – apparently to scare their potential victims.”

• “Potential victims may be told they are entitled to big refunds, or that they owe money that must be paid immediately to the IRS. When unsuccessful the first time, sometimes phone scammers call back trying a new strategy.”

• “Scammers use fake names and IRS badge numbers. They generally use common names and surnames to identify themselves.”

Tax officials said the IRS always sends notices of unpaid taxes via U.S. mail and never asks for credit card, debit card or prepaid card information over the phone.

In Whalen’s case, the caller used a Washington, D.C., phone number that continued working after Whalen transferred $3,845 via prepaid cards and reported the crime to the Sheriff’s Department. Whalen said she called “Officer Keith” back to voice her anger and frustration.

“I know this is a scam,” Whalen told the woman. “You’re a criminal, and criminals make mistakes. And some day you will be caught.”

The Sheriff’s Department is investigating the complaint. However, federal officials say money sent to IRS imposters is often impossible to retrieve.

Contact the writer: kkyle@ocregister.com or on Twitter @keegankyle