Labour has admitted it made an error in the initial release of its GST policy, but insists its numbers do add up.
The party has promised to cut GST from fresh and frozen fruit and vegetables from April next year if re-elected.
A fact sheet sent to media under embargo before yesterday's announcement calculated the four year cost of the policy at just shy of $2 billion.
The figure was quietly updated to $2.2 billion at the actual reveal, but media were not advised of the mistake or correction until the National Party alerted them today.
National's deputy Nicola Willis says it is an amateur school-boy error by Labour.
Labour's leader Chris Hipkins acknowledged the wrong data set was included in early documentation.
But he says any claims of a fiscal hole are false.
The policy is believed to be popular with voters - with a previous poll putting more than three quarters in support.
But the details are still being digested, including the promised savings of just 4 or so dollars a week for the average shopper.
Voters may be mixed in their opinions but there is far more consensus among economists and tax specialists, who are near unanimous in their opposition.
