The planned Accident Compensation Corporation (ACC) building in Dowling St, between Queens Gardens and the Exchange, was first expected to be completed by next year.
Now the developer, Ngāi Tahu Property, says it is more likely to be completed in the middle of 2025.
A Ngāi Tahu Property spokeswoman said site enabling works took longer than anticipated.
Piling had been completed and foundation work was now under way at the site, she said.
Ngāi Tahu Property expected structural steel and concrete precast wall panels to be installed from August of this year.
"Based on the current progress, the project is expected to be completed around mid-year of 2025," the spokeswoman said.
The delays on the project were due to "the number of archaeological finds, removal and remediation of contaminated land", she said.
She did not elaborate on the nature of the archaeological finds, or the contaminated land.
As work got under way, the Otago Daily Times reported remnants of the Standard Insurance Company building and Sargood, Son & Ewen’s boot factory — both from the 1870s — were visible as excavators uncovered the heart of Dunedin’s early commercial development, but also, before that, a place for waka landing, food gathering and trade.
Archaeological discoveries were being recorded and managed by New Zealand Heritage Properties, a Ngāi Tahu spokeswoman said at the time.
Heritage New Zealand referred comment to the developer.
