No code compliance certificate for the wall was ever issued, council building solutions manager Paul Henderson said.
A certificate was issued for a culvert in the Gladstone Heights subdivision, and for a house built by the couple there, but the unconsented wall was added by the developer after the culvert was signed off, he said.
The wall is at the centre of a dispute between Irwin Logan Dr homeowners Himanshu Dua and Renu Anand, subdivision developer Gladstone Heights Ltd and the city council.
Fixing it could cost the couple up to $100,000 or a fine of up to $200,000 if they do not, but structural engineer Bruce Chisholm has raised concerns about the problem being dumped on the couple.
Mr Chisholm called on the council to withdraw a notice requiring the landowner to fix the wall and to impose it instead on the developer.
The developer has said any problem with the wall was not created by the company.
The council was asked about code compliance on Wednesday and Mr Henderson yesterday clarified the certificate was issued for the original culvert in June 2018.
"The retaining wall was built later, sometime between June 2018 and December 2018, without a building consent and without DCC knowledge."
The couple bought the property in September 2018.
Mr Henderson said a separate compliance certificate was issued for the house in November 2019, but, again, this did not include the retaining wall.
