Issues in relation to which referendums are mandatory at the national level

New Zealand
Answer
None
Source
Referenda (Postal Voting) Act 2000;
(Enacted on 14 November 2000)
Electoral Act 1993
(Enacted in 17August 1993, last amended in 1 July 2012)
http://www.legislation.govt.nz/act/public/1993/0087/latest/DLM307519.html
Comment
Legislation provides only foroptional referendum and citizen initiative.