The general manager of stamps and coins at New Zealand Post, which designed and printed the stamps, told TV3 on Tuesday that the design had been approved Queen Elizabeth II.
Ivor Masters described the design as innovative. He said the stamps were collectors items so it was very unlikely they would be torn apart for postage.
The item features a single image of Kate and William standing side by side on two stamps of different values. Ripping along the stamps' perforations would tear the royal couple apart.
New Zealand and Niue are Commonwealth nations.