Identification

All passengers - including those who are not required to have a passport or visa - must be able to show identification with an officially approved document, which indicates nationality, at the check in-desk or at the terminal security control. Passengers are responsible for finding out about passport and visa requirements. Viking Line can refuse to carry anyone who does not possess the necessary documents.

Please note that going ashore in Estonia or Latvia only is permitted during the regular opening hours of border control authorities. For example, this means that passengers many not go ashore at night time.  

Finnish Police, Customs and Border guard press release:
Finnish authorities highlight importance of appropriate travel documentation (PDF 39 Kb) »