IT developers

The filing types that can be sent to the Finnish Tax Administration in electronic format include Annual Information Returns, Self-assessed tax returns (formerly the Periodic tax return), and Income Tax Returns.

The Katso secure sign-in service is available for ensuring the secure identification of the user and for verification of the user's authority. The party that sends off a tax return form electronically to the Tax Administration must have Katso identifiers. From this follows that the software program generating the files must be compatible with the Katso system.

  • Katso authorisations are no longer valid starting 1 January 2021. If you are currently using Katso authorisations to take care of someone else’s tax matters, you must request new Suomi.fi authorisations instead. Your Katso authorisations will not be automatically replaced with Suomi.fi authorisations.

  • When using your Suomi.fi authorisation, log in to the e-service with your personal e-bank codes, a mobile certificate or a certificate card. The mobile certificate or certificate card can also be provided to you by an organisation.

The materials for creating an inbound file must comply with the specifications published by the Finnish Tax Administration. The complete file must match the applicable format requirements. The system checks the files during the data transfer process.

Inbound files can be transmitted via the Ilmoitin.fi web service. Access to Ilmoitin.fi can be arranged as a direct software interface or via the ilmoitin.fi website.

The Finnish Tax Administration updates its file specifications regularly at different times of the year, depending on the types of filings. Software developers must carefully follow the currently valid specifications, requirements and time schedules for e-filing.