The IRS has a Criminal Investigative Division that is in charge of investigating taxpayers of wrongdoing and recommending prosecution of those people to the Department of Justice.
Of all the taxpayers that were criminally prosecuted in 2014, the Criminal Investigation Division claimed a 93.4% percent conviction rate. Further, this conviction rate was the highest conviction rate of all federal law enforcement agencies in 2014. The Criminal Investigation Division initiated 4,297 cases in 2014, a 19% decrease from 2013. The Criminal Investigation Division has 2,402 special agents and staff, although this figure is down 29% since 1995.
In 2014, the Criminal Investigation Division handled the largest criminal tax case ever filed, against Credit Suisse, in which the bank pled guilty to conspiracy to aid and assist U.S. taxpayers in filing false income tax returns. Credit Suisse agreed to pay a total of $2.6 billion dollars as a result of its guilty plea.
If an IRS Special Agent contacts you about your taxes, it is probably because you are under criminal investigation. Special Agents typically travel in pairs so that one can testify against you if the story you told suddenly changes. Special Agents typically read you your Miranda rights, also known as the right to remain silent. You have the right to not talk to the Special Agents and to first seek legal counsel before answering any questions.
Considering the conviction rate by the IRS Criminal Investigative Division, is it wise to not answer any questions until you have sought legal counsel regardless of how skilled you think you are in the situation.