INDIANA, (WOWO): Officials with the IRS are warning consumers about what they’re calling the largest scam in their history.

So far, about 20,000 Americans have been bilked out of more than $1 million. The IRS says the scam involves crooks claiming to be IRS agents. They call people up and demand immediate credit or debit card payments on taxes owed. They say the scammers often have the last four digits of the victim‘s Social Security numbers and the number they‘re calling from looks like it could be from the IRS. They also include a follow up email from a fake IRS website.

Leaders with the IRS say they don‘t call people demanding payment. They generally send out a letter first and consumers should be extremely careful about releasing their personal information.