A mobile trader has pleaded guilty to 16 charges, as the Commerce Commission cracks down on the sector.
The charges relate to Best Buy's door-to-door sales business in Auckland and small North Island towns.
Mobile traders - also known as truck shops - are companies that mainly operate by selling household goods door-to-door or from trucks parked in the street.
The commission said Best Buy sold items like electronics, perfume and mowers, often on credit, and at "significantly higher prices than mainstream stores".
Eleven charges related to failing to give customers information, such as the number of payments needed and their cancellation rights.
The other five related to contracts that could have misled customers into thinking Best Buy had the right to repossess goods when it did not.
Best Buy will be sentenced later this year.
The commission said 11 mobile traders were prosecuted last year, and five of them were fined more than $500,000 between them.