As specified by the Kieswet, the law governing elections, any registered party can deliver a list of candidates (see this question for details) in each district (kieskring)¹.
When people cast their vote, they vote for:
- A list (in the example, numbered 1–28).
- (optional) Preferentially for a candidate on that list. If a voter chooses a list but no candidate, their vote goes to the first candidate on that list.
In the example ballot, candidates are not explicitly named; in the Dutch general election 2017, district 's Gravenhage, there are a record total of 881 candidates. This ballot design is new; previously and for elections with less candidates, all candidates were/are explicitly named on the ballot paper.
If a list receives enough votes to have at least one elected candidate, the law specifies that seats are assigned as follows:
- Candidates who receive more votes than the preferential threshold (voorkeursdrempel; either 25% or 50% of the electoral threshold² depending on the election) are elected first, sorted by the number of votes they have received. In practice, this always includes candidate number 1, although theoretically it is possible that all voters for a party declare their preference for lower numbers, this has never happened.
- The remaining seats are assigned to candidates who receive less than the preferential threshold, sorted by their position on the list as registered by the Kiesraad.
For example: suppose that 60,000 votes are required per seat and a party has received 600,000 votes, enough for 10 seats. Suppose that nr. 1 has received 500,000 votes, nr. 5 25,000 votes, nr. 12 50,000 votes, and all other candidates less than 15,000 votes. Then the order in which candidates are elected will be:
1: nr. 1
2: nr. 12 (this candidate enters parliament thanks to preferential votes)
3: nr. 5 (candidate nr. 5 would have been elected even without preferential votes, so the votes are relevant only symbolically)
4-6: nr. 2-4
7-10. nrs. 6–9
On average, this tends to happen for some 1–2 candidates at each general election.
¹There is no requirements for a person to live in the district where they are a candidate, and it is permitted to be a candidate in more than one district. In practice, most parties deliver lists that are mostly or entirely identical between districts.
²The electoral threshold in The Netherlands is equal the number of votes required for one seat. In general elections, for the national parliament with 150 seats, this is 1/150th of the number of valid votes cast.