IF you get any phone call from the IRS. with one exception, it is a SCAM.
That exception is if you call them and REQUEST a call back.
There is another scam where they call you and tell you they are giving out an award for being a good citizen,, all you need do is send them a security deposit.
(Took me a long time to get to the point where they ask for that)... Guess what, Federal law says if they tell you YOU HAVE WON, they can not ask you for any kind of front money to send you the prize.. It is a scam.
If you think bank robbers are bad... Well the annual take from robbery, all kinds of robber, would be a very slow month in the SCAM business.