Any persons that has to abide by any TAX law which forces them to cover the debts of higher societal ruling class.

A worker who pays a high percentage of his/her salary to the government. A tax slave isn't a slave, per se, just someone who perceives that they pay more in taxes than they receive in benefits. That said, people who perceive themselves as tax slave don't always take into account public benefits like roads, water, electricity and other infrastructures supported by their payments to a governing body.