The loss compares to a $186m profit in the prior financial year.
Z chief executive Mike Bennetts said the full-year result highlighted the competitiveness of the retail fuel market and the severity of the low refining margins it saw in the last quarter.
Bennetts said the onset of Covid-19 had created unprecedented conditions with a high degree of uncertainty for many businesses.
"The Covid-19 global pandemic is presenting numerous operational challenges, not least a material decline in demand for product. Z continues to respond well to these challenges and has acted swiftly to reduce operating costs, increase cash flow and provide flexibility to the balance sheet that will position Z well for the expected improvement in post-Covid trading conditions."
He added that lockdown has been particularly hard on the business.
"The New Zealand lockdown and subsequent progression through alert levels has very significant implications for customer demand levels, the mix of fuel required and overall market competitiveness. Consumer demand has been meaningfully impacted during the lockdown period and the associated economic effects of Covid-19 on employment and income are likely to be much longer lasting."
He said during the first four weeks of lockdown under level 4 Z had seen an 80% reduction in retail fuel volumes sold, an 85% decline in jet volume and 60% fall in commercial fuel sales.
