Latte31-I remember that case. I know that people that work in the United States but keep their money in a foreign bank accounts and avoid paying federal income taxes on that money are committing offshore tax evasion.
Likewise if an American is a working abroad they will have to pay federal income taxes to the United States as well.
The IRS offers various penalties but the criterion for the consideration of tax evasion is the intent to defraud the government. Intentionally avoiding paying federal income taxes is classified as fraud and the penalties include incarceration and substantial fines and restitution of back taxes.
The IRS is really not an agency that you want to owe money to. Tax evasion law is pretty specific and often tax evasion lead to jail.