A district court judge has ordered a mobile truck shop operator to pay $126,000 in fines.
Macful International Ltd, trading as Ezitruck Shopping, has been found guilty of 16 charges.
The court found Ezitruck breached the Credit Contracts and Consumer Contracts Act (CCCFA) by failing to disclose key information in contracts or register as a financial services provider.
"The CCCFA is there to protect consumers and is of the utmost importance for good commercial management throughout the country, and for that reason the breaches are considered serious," Judge Noel Sainsbury said.
The offending occurred in the second half of 2015 when the company entered into about 3000 contracts for household goods bought through its truck shop and paid for over a period of time.
Ezitruck failed to include in the contracts accurate payment details or descriptions of securities taken.
The company also failed to register as a financial service provider or join an approved dispute resolution scheme as required under the CCCFA.
Anna Rawlings from the Commerce Commission said she welcomed the sentence.
"The contracts were difficult to read and the key information was obscured.
"This meant the documents failed a basic requirement of the law, which is intended to assist borrowers to understand what they are signing up to."
The judge ordered Ezitruck to refund costs of borrowing the customers paid for and were barred from receiving any further credit, default or dishonour fees from contracts entered into during that period.
Ezitruck Shopping was one of 11 operators prosecuted after a Commerce Commission investigation.
The prosecutions have resulted in $1.1 million in fines given to mobile traders.
The investigation followed years of accusations of mobile traders unfairly preying on vulnerable people in lower socio-economic areas.
Only one of the 32 truck shops visited by the commission during the year-long investigation was found to be complying fully with the law.
Mobile trader Zee Shop, brought to the commission's attention after the 2014/15 investigation, was fined $108,000 for its unclear contracts earlier this week.