If you reached 22 years of age after 1 September anytime on or after 1 September 2006 then you automatically lost your Norwegian citizenship on your 22nd birthday if you:
You do not lose your citizenship, however, if you have applied to retain your Norwegian citizenship and you have received a letter of decision from UDI affirming that you were allowed to retain your Norwegian citizenship after reaching 22 years of age (retention of citizenship).
If you acquired Norwegian citizenship after you were born because you or your parents either applied for, or submitted notification of, citizenship on your behalf, acceptable documentation may include:
If you became Norwegian because you were adopted by a Norwegian citizen:
If you automatically acquired Norwegian citizenship when your parents entered into marriage (applies only if you were born before 1 September 2006), then you must provide:
If you had no other citizenship than Norwegian when you reached the age of 22, then you must document that you hold a residence permit in the country where you live (does not apply if you reside in Norway). If only one of your parents was Norwegian when you were born, then you must also document that you have not acquired citizenship in the country where your other parent is a citizen.
Documentation that shows that you are not a citizen in your country of residence:
Documentation that shows that you are not a citizen of your other parent’s country of residence (if only one of your parents was Norwegian when you were born):
If you have resided in Norway for a total of two years before reaching the age of 22:
If you have resided for a total of seven years in Norway or in other Nordic countries before reaching 22 years of age, you must submit:
If you have received a letter of decision affirming that you are allowed to retain your Norwegian citizenship (retention of citizenship), you must:
"The Norwegian Nationality Act of 10 June 2005".