Permanent residents are being reminded by the Government that rules around gaining citizenship are changing next month.

Internal Affairs Minister Nathan Guy said from April 21 all permanent residents who apply for citizenship must have been in New Zealand for five years, rather than three.

In 2005 the period was extended to five years, but a transitional window was created where some people could still apply under the old three year requirement. This period is now ending.

"Becoming a New Zealand citizen is an important milestone in people's lives, and I don't want to see people losing their eligibility for up to two years because they missed the deadline. Eligible people who want to be considered under the old three year rule must ensure that their application is received by the Department of Internal Affairs' Citizenship Office by April 20, 2010," said Mr Guy.

People are eligible to qualify for the three year period if they were permanent residents before April 21, 2005, or had their successful application for permanent residency accepted by Immigration New Zealand before that date.