Audits carried out by Customs have resulted in $48 million being collected for the Crown in just over 18 months.
Customs Minister Maurice Williamson said Customs' trade assurance arm works to verify that import and export entry data is accurate, and to ensure correct revenue is collected.
Revenue includes duty and GST paid on imported goods, together with excise and excise equivalent duty which is payable on tobacco products, fuel and alcohol products.
"In the financial year to June 2012 audits resulted in $31 million in additional revenue being collected. This financial year, trade assurance has accounted for an additional $17 million.
"These amounts are well above the targeted figure of $15 million a year and shows systems Customs has in place are working well," Mr Williamson said.
When detected, a shortfall in paid revenue results in formal assessment notices being issued in accordance with the Customs and Excise Act provisions.
Often the cause of short paid revenue is attributed to error or oversight. If Customs suspects fraudulent activity then further action is taken, which sometimes leads to prosecution.
"New Zealand's trade activity is worth an estimated $90 billion a year, and Customs contributes about 15 per cent of government revenue through duties and excise."
$11.3 billion in Customs revenue was collected in the 2011/12 fiscal year.