There are many "IRS" scams right now. The IRS will not call you, they will not threaten to send you to jail for failure to pay over the phone, they will never ask for iTunes cards or any other gift card forms of payment. If they call, simply hang up on them.
The IRS will not send you an email if you owe taxes. They will send you a letter in the mail. Scammers are now sending fake letters that look similar to actual IRS letters. If you receive any communication from the IRS, bring it in to be reviewed.
A new scam that is circulating is one where the caller will state that you Social Security Number has been compromised, or even been linked to crimes committed. Do not give out your social security number to anyone that calls, and do not pay them any money to "clear" your social security number.