Iceland generally imposes full tax liability if you stay in Iceland for more than 183 days in any 12-month period. Certain normal temporary absences, such as vacations, may also be included under Icelandic tax rules. Use this rule as a day-tracking guide and confirm your individual tax residency status with the Icelandic tax authorities or a tax adviser.
https://www.skatturinn.is/einstaklingar/skattskylda/almenn-skattskylda/