Stanley Cohen was sentenced yesterday in federal court in Syracuse, New York, after pleading guilty to impeding the US tax agency and failing to file tax returns.
He has said a trial and any appeals would have been a "tremendous" financial burden and called the prosecution a witch hunt.
Prosecutors say Cohen filed no tax returns for six years, requested a filing extension each year and made modest payments toward taxes due.
In September, Cohen's client Sulaiman Abu Ghaith received life in prison for acting as the voice of al-Qaida after the September 11 terror attacks.