A rise in imports has pushed the trade balance into deficit.
Just released official figures show a shortfall of $774 million last month, the largest for a July month in five years.
Exports fell 5% to $3.8 billion, led by a decrease in volumes of crude oil, milk powder, butter and cheese.
Imports jumped 17% to a record $4.6 billion for a July month, with more than a third of the increase due to aircraft and parts, and another third coming from crude oil.
On an annual basis, the trade deficit stood at $1.7 billion.
Stronger consumer spending is also reflected in the figures, with a rise in demand for cars.
Statistics New Zealand says a deficit is not unusual for this time of year, with eight of the last ten years being deficit years.
Westpac senior economist Michael Gordon says the deficit is partly a payback for a better than expected balance in June.
He says imports bounced back in July after a soft June.