The woman who investigated complained to the Real Estates Agents Authority for the false advertising.
The Authority heard that the agency genuinely believed the flat was legally established and was unaware of the building permit because it was not printed in the Land Information Memorandum.
The agency said as soon as it learned of the permit it cancelled the open home, ordered the "home and income'' sign to be removed and withdrew the property from sale.
In the Authorities findings released yesterday it acknowledged the immediate steps the agency took after it discovered the permit and that the conduct was not intentional.
However, the Authority ordered the agency to undergo training because its conduct indicated a lack of knowledge of important aspects of real estate practise, pay $500 to the Authority, and was reprimanded.