Caller says they are from IRS & must return call to avoid trouble.

It is NOT the IRS ---just a scamming thief in India or Pakistan.  No need to return the call.

The real IRS mails letters if there is a problem.

I just got this call as well from 301-960-3061 saying you must call this number as this is the IRS, call immediately to avoid legal action from the IRS and it was automated not from a person but a machine.

Recording supposedly from the IRS stating it is important that I return the call to a number in the 301 area code.  The number was repeated twice.  Since I had no way to write it down, I don't recall it.  The call ended with a cheery "goodbye.."  I agree it must be a hoax to elicit people to divulge their private info or send money.  I  plan to file a police report.

I guess you are right in your suspicion.