You can submit a transit declaration in the Customs Transit Declaration Service on the customs website or with an EDI or XML message.
You don’t need permission from Customs to use the Transit Declaration Service. You can fill in the declaration as an unidentified user, then the declaration is not saved. However, the declaration is saved when submitted by a user who has been identified through Suomi.fi.
For EDI or XML message declaration you need a system and a customs authorisation for message exchange. In the future, the only message format will be the XML message.