Immigration New Zealand says it is working to keep up with new ways being devised by prospective immigrants to cheat on their visa applications.
It said imposters have taken English or medical tests on behalf of other people and fabricate or manipulate documents to falsify qualifications or work experience.
Immigration New Zealand operations manager Michael Carley said in a recent case, a Chinese man who was applying for a business investor visa to bring his family to New Zealand used someone else to sit his English language test.
In that case, immigration staff noticied the picture in his British Council test did not match the photo in his passport.
Mr Carley said The British Council, where he had sat the test, conducted an independent investigation and concluded the certificate was not authentic.
"This case really shows the value of a competent immigration officer who has got some experience and of course our people see a number of similar documents, so they get pretty good when dealing with particularly the main nationalities of what they should be seeing and what someone altered might look like."
Mr Carley said it was using approved doctors and interviews with applicants to target frauds in which an imposter was used to sit a test.
"There's a number of risks around imposters and that is really about getting someone else to front for you, whether it's a medical test, whether it's doing English language."
Mr Carley said in the context of 30,000 residence applications a year the cases of suspected fraud were a small proportion, but they run to several hundred a year.