The IRS will not:
Call you to demand immediate payment. The IRS will not call you if you owe taxes without first sending you a bill in the mail.
Demand that you pay taxes and not allow you to question or appeal the amount you owe.
Require that you pay your taxes a certain way. For instance, require that you pay with a prepaid debit card.
Ask for your credit or debit card numbers over the phone.
Threaten to bring in police or other agencies to arrest you for not paying.