Major Bay of Plenty employer Whakatāne Mill has decided to proceed to close its doors.
It employs just over 210 staff and has produced paper and packaging products, lately mostly for export, for more than 80 years.
Its management said all staff would be made redundant, with most completing their roles by the end of June.
The company would cease production on 21 June and then begin the decommissioning of the plant, with an expected final closure date of 30 June, it said.
A number of options were being explored for both the plant and the site, but no decisions had yet been made.
Whakatane Mill Limited general manager Juha Verajankorva said the decision was not an easy one.
"This is a very tough day for all of us, and we will work to do the best we can by our people and the community of Whakatāne and the Bay of Plenty as we complete our decommissioning and closure of the plant," he said.
"Our focus at this time is caring for our staff and we will continue to work with union representatives and other agencies to support our people through the redundancy process."
The mill proposed the closure last month after losing its biggest customer, Swiss packaging company SIG Combibloc, which accounts for 80 percent of its sales.
"It's very tough, but SIG's decision is understandable, given the circumstances and the reality that we cannot compete with suppliers elsewhere. We accept that further investment in the business is just not feasible," he said.
The business is no longer considered economic.
"The volumes we produce are modest by global standards, and our costs-per-unit can no longer compete."