Must GST charged on sales be explicitly mentioned on the commercial invoice / customer receipt (a breakdown of the total) or can the vendor state, for example: ‘NZD 500 total price of the product (GST included)’?

The commercial invoice / customer’s receipt should provide an indication of which goods have had GST charged. For example, if GST is charged on everything listed on the receipt, the supplier can provide this indication by either showing the amount of GST on each line item or stating the total price and a statement that it includes GST.