Truck wages are wages paid not in conventional money but instead in the form of payment in kind (i.e. commodities, including goods and/or services); credit with retailers; or a money substitute, such as scrip, chits, vouchers or tokens. Truck wages are a characteristic of a truck system, and are banned by the labour legislation of many countries.
"Truck", in this context, is a relatively archaic English word meaning "exchange" or "barter".