There is a scam making the rounds, targeting South Florida taxpayers over the phone with threatening calls from supposed IRS agents. But, according to the Internal Revenue Service, there's a foolproof way to know you're dealing with the real thing.

You can call the IRS back at 1-800-829-1040.  They can verify the name and badge number.  Anybody calling from the IRS should be able to give you their badge number and their full name. 

Also, a big clue: An IRS spokesman says agents will never use threats or be rude, which is what these callers are apparently doing, in an effort to get your financial information.