How is the national electoral register created?

Cook Islands, Electoral Act 2004, accessed 1 October 2022

10. Electoral Registration Office - (1) There shall be commissioned by the Minister, an Electoral Registration Office within the Ministry of Justice for the purpose of administering this Part of this Act.

(2) The Secretary of Justice shall provide the office with appropriate office space, adequate furniture, fixtures and relevant logistical support.

11. Chief Registrar of Electors - (1) The Registrar-General of Births and Deaths or his or her nominee stationed in Rarotonga, shall be the Chief Registrar of Electors and shall be charged with the duty of carrying this Part of this Act into effect. […]

(4) Throughout the conduct of any election the Chief Registrar of Electors shall provide the Chief Electoral Officer with such assistance as may be required.

Elector's Guide provides information about how voters get registered.

It has to be noted that the Electoral Registration Office is a separate entity independent of the Electoral Office. Since both entities are governmental, we treated the Electoral Registration Office as EMB.