Solid Energy will go from being the country's largest coal producer to 35 people in an office at the end of next month, when its major remaining assets are sold.
The chief executive, Tony King, said the sale of the Stockton operation and the two Waikato mines, Rotowaro and Maramarua, have been approved by the Overseas Investment Office.
He said the company had been in administration since August 2015, and the sale effectively signalled the beginning of its winding down.
"It's been a long time coming and I think for many of the people who are going to be here at the end, it will be with a sense of relief as much as sadness to have finally dealt with all of these remaining matters."
Mr King said most employees and contractors would transfer to the new owner, BT Mining, a consortium of Bathurst Resources and Talleys Energy Limited.
