Fire and Emergency says Covid-19 cost it lost revenue of $42 million, some 7 percent of its income.
The information came in the department's post-election briefing to its incoming minister.
It said it sought to make up for the loss by cutting travel and non-operational training, and reducing its capital expenditure.
Even so, it expected to be in a deficit of $12 million as a result.
The briefing said any further reduction in income would require financial support from the Crown.
Fire and Emergency gets its revenue mainly from a levy on insurance premiums.