If you're separated or not married, the father can declare paternity during the pregnancy, in connection with the birth, or after the birth. 

The Tax Administration receives and processes paternity declarations.

Declaring paternity online

Paternity can be declared online by both parents identifying themselves using a secure electronic ID and signing a digital declaration. You must fulfil certain critera to declare paternity online. You can find the criteria on NAV’s website.

You can declare paternity online here

Declaring paternity in person

The father may declare paternity by personal attendance:

• At the tax office. Remember to book an appointment in advance.
• At a NAV office.
• With a judge at the district court.
• At the midwife’s or doctor’s office in connection with the birth.
• At a posted foreign service official’s location if the father is abroad.

Remember to bring valid identification to your appointment.

If the person who has declared paternity is not stated as the father in the birth notification, the mother must approve the paternity.