The Privacy Commissioner is warning people they do not have to fill in a survey sent to them by New Zealand Post.
The state-owned enterprise is sending a six-page survey to 1.6 million households in an effort to counter falling postal volumes because of the recession.
NZ Post has shed almost 500 jobs this year because of a 7% fall in domestic mail traffic.
The survey asks for detailed personal information.
Privacy Commissioner Marie Shroff says she has been fielding questions from people who are confused about whether it is compulsory to participate.
She says people can chose whether to take part, but should be aware their details will be passed to businesses and marketers both here and overseas.
She describes the questions as very personal.