Open list, using d'Hondt method.
Finland, Constitution 1999 (rev. 2011), accessed 17 April 2019
Section 25. Parliamentary Elections
The Representatives shall be elected by a direct, proportional and secret vote. Every citizen who has the right to vote has equal suffrage in the elections.
For the parliamentary elections, the country shall be divided, on the basis of the number of Finnish citizens, into at least twelve and at most eighteen constituencies. In addition, the Åland Islands shall form their own constituency for the election of one Representative. […]
Finland, Vaalilaki [Election Act], 2.10.1998/714, (amendments up to 361/2016 included), accessed 17 April 2019
Section 6. Division of parliamentary seats between electoral districts
With the exception of the electoral district of Åland, a total of 199 representatives are elected by proportional vote in the other electoral districts. In the electoral district of Åland, one representative is elected as provided below.
With the exception of the electoral district of Åland, the division of parliamentary seats is carried out on the basis of the number of those Finnish citizens who, according to the Population Information System, had their municipality of residence in Finland in the electoral district in question on the last day of the calendar month six months before the election day. Changes in the municipal division entering into force in the beginning of the election year shall be taken into account in the division of parliamentary seats. The division is carried out by dividing the number of Finnish citizens in each electoral district by the combined number of Finnish citizens in all electoral districts and multiplying this number by 199. The number of parliamentary seats for each electoral district corresponds to the whole number derived from this calculation. If all seats are not divided in this manner, the remainder of the seats are divided in descending order between the electoral districts according to the decimal fractions derived from the calculation. (1263/2007)
The Government carries out the division in good time before parliamentary elections by issuing a decision to be published in the Statute Book of Finland.
Section 76 (496/2013). Voting on election day
A voter has in parliamentary elections and municipal elections the right to vote for a candidate in the master list of candidates for the electoral district or municipality in which the voter is registered as eligible voter in the election in question, in elections to the European Parliament to vote for a candidate in the master lists of candidates, and in the presidential election to vote for a candidate in the list of presidential candidates. (563/2015)
The voter shall mark the number of the candidate he or she is voting for in the ballot in such a manner that there can be no uncertainty as to whom he or she has voted for. The marking shall be made in a voting booth or, if this is not possible without causing undue difficulty to the voter, somewhere else in a manner that maintains the election secrecy.