Correct. Customs don't chase people for payment. You don't pay, you don't get your stuff. Whatever shipping agent you are using will hold the goods and calculate the amount you need to pay. If they need the lodge a formal clearance with Customs (low value items are written off on mass via manifests) then Customs charge additional processing fees on top of the duty/GST and then there will be the Customs Agents fees. If MPI (MAF) decide to examine your shipment, or an MPI clearance is required, there can be additional charges. Customs do not charge you for examining your goods.