Some people say it depends on how much you actually owe on your IRS Federal taxes in order to serve jail time. Does anyone know the MINIMUM amount?
As is usually the case, "Somebody" is wrong.
Not paying tax is not a crime. Filing a fraudulent return or committing tax evasion is a crime, and failure to file a return in and of itself does not constitute tax evasion. Nobody goes to prison merely because they owe taxes, regardless of the amount owed.
The IRS has a vested interest in keeping you OUT of jail, actually. Prisoners don’t earn enough in prison wages to be able to pay anything towards their debts. They’d rather see you earning income that they could then go after to satisfy the debt.