Criminals are posing as Internal Revenue Service agents in hopes of stealing money or personal information for unsuspecting victims, the IRS said in a warning to taxpayers Tuesday.

The agency is asking taxpayers to stay vigilant against phone scams as the April filing deadline approaches.

Phone scams or “vishing” (voice phishing) continue to pose a major threat, officials said. The scam has cost thousands of people millions of dollars in recent years, and the IRS continues to see variations on these aggressive calling schemes.

Phone scams again made the IRS’ “Dirty Dozen” list this year, the agency’s annual compilation of some of the schemes that threaten taxpayers not only during filing season but throughout the year.

The IRS is highlighting each of these scams on consecutive days to help raise awareness and protect taxpayers. The IRS also urges taxpayers to help protect themselves against phone scams and identity theft by reviewing safety tips prepared by the Security Summit, a collaborative effort between the IRS, states and the private-sector tax community.

“Taxpayers should be on the lookout for unexpected and aggressive phone calls purportedly coming from the IRS,” said IRS Commissioner Chuck Rettig.

“These calls can feature scam artists aggressively ordering immediate payment and making threats against a person. Don’t fall for these,” Rettig said.

Beginning early in the filing season, officials noted the IRS generally sees an upswing in scam phone calls threatening arrest, deportation or license revocation, if the victim doesn’t pay a bogus tax bill.

The calls most often take the form of a “robo-call” (a text-to-speech recorded voicemail with instructions to call back a specific telephone number), but in some cases may be made by a real person.

These con artists may have some of the taxpayer’s information, including their address, the last four digits of their Social Security number or other personal details, officials said.

The Treasury Inspector General for Tax Administration, the federal agency that investigates tax-related phone scams, reported these types of scams have cost 14,700 victims a total of more than $72 million since October 2013.

How the scams work

Criminals make unsolicited calls and leave voicemails with urgent callback requests claiming to be IRS officials. They demand that the victim pay a bogus tax bill by sending cash through a wire transfer, prepaid debit card or gift card.

Many phone scammers use threats to intimidate and bully a victim into paying. The phone scammers may alter or “spoof” their caller ID to make it look like the IRS or another agency is calling. The callers may also use IRS employee titles and fake badge numbers to appear legitimate.

The IRS also reminds taxpayers that scammers often change tactics. Variations of the IRS impersonation scam continue year-round and tend to peak when scammers find prime opportunities to strike. Tax scams can be more believable during the tax filing season when people are thinking about their taxes.

Tell-tale signs of a scam

Here are some things the scammers often do, but the IRS will not do. Taxpayers should remember that any one of these is a tell-tale sign of a scam.

The IRS will never:

• Call to demand immediate payment using a specific payment method such as a prepaid debit card, gift card or wire transfer. Generally, the IRS will first mail a bill to any taxpayer who owes taxes.

• Threaten to immediately bring in local police or other law-enforcement groups to have the taxpayer arrested for not paying.

• Demand that taxes be paid without giving taxpayers the opportunity to question or appeal the amount owed.

• Ask for credit or debit card numbers over the phone.

• Call about an unexpected refund.

For taxpayers who don’t owe taxes or don’t think they do:

• Report IRS or Treasury-related fraudulent calls to phishing@irs.gov (Subject: IRS Phone Scam).

• Do not give out any information. Hang up immediately. The longer the con artist is engaged; the more opportunity he/she believes exists, potentially prompting more calls.

• Contact TIGTA (the Treasury Inspector General for Tax Administration) to report the call. Use their IRS Impersonation Scam Reporting web page. Alternatively, call 800-366-4484.

• Report it to the Federal Trade Commission. Use the “FTC Complaint Assistant” on FTC.gov. Please add “IRS Telephone Scam” in the notes.

For those who owe taxes or think they do, call the IRS at 800-829-1040.

Taxpayers can view tax account information online, and see their past 24 months of payment history, payoff amount and balance of each tax year owed.

For more information, visit Tax Scams and Consumer Alerts on IRS.gov.