You must register your stay in Finland if you are a citizen of the European Union and your stay in Finland exceeds three months. Fill in and pay for your application here and visit the Finnish Immigration Service to verify your identity within three months of entering into Finland. For registration purposes, citizens of Liechtenstein and Switzerland are considered EU citizens.
If you are a citizen of Denmark, Iceland, Norway or Sweden, you don't need to register. Instead please visit your Local Register Office.
A family member of an EU citizen that resides in Finland for over three months and is not a citizen of the Union can apply for a residence card of a family member of an EU citizen. The card must be applied for within three months of entering into Finland.
If you are the family member of a Finnish citizen but you haven't lived together in another EU country, in most cases you should apply for a residence permit instead.
As of January 1st 2017, all residence matters of EU citizens and their family members are be handled by the Finnish Immigration Service.