After pleading guilty to conspiring to impede the functions of the Internal Revenue Service, Russell Mahler, a 78-year-old from Clinton, Conn., was sentenced to 18 months in prison and ordered to pay a $40,000 fine.

Mahler, who owns a chain of six gas stations, admitted that he had paid substantial portions of his employees’ wages in cash and then did not report the income to the IRS, resulting in a total tax loss of $247,000.

Mahler’s son and business partner pleaded guilty to the same charges. He received a sentence of one year and a day in prison.

What’s more, Mahler admitted that he also tried to evade about $46,000 in personal income taxes. He faces up to three years in prison and a $100,000 fine. Mahler has also been ordered to pay all back taxes.