The committee's decision said there were conflicting views over what advice the buyers, who were not named, were given by Mr Jarden.
The buyers said they asked at a viewing whether the property extended to the fenceline, and Mr Jarden confirmed it did.
However, Mr Jarden said there were no questions asked about the boundary.
There were also conflicting views on whether Mr Jarden knew of the boundary encroachment, however he said he was aware the previous owners had been asked to move a vegetable garden inside the boundary, as it had been on DoC property, the decision said.
The committee said encroachments into the estuary were common, and real estate agents working in the area should have been aware to check on boundaries.
While acknowledging the buyer had a responsibility to make their own enquiries, the committee said the agent should have ensured the property was accurately described.
The complainants had asked that the commission be returned and the property be auctioned, with the agent to make up any loss from their original purchase price.
The committee declined and made no order for compensation. Mr Jarden was fined $5000, censured, and ordered to pay the complainants $1778 for legal costs and $1301 for survey costs.
As he was retired, nobody from the real estate office he worked at in Paraparaumu was able to comment.