Compulsory voting
Countries that have compulsory voting by law but do not enforce it:Although voting in a country may be compulsory, penalties for failing to vote are not always strictly enforced. In Australia and Brazil, providing a legitimate reason for not voting (such as illness) is accepted. In Argentina, those who were ill on voting day are excused by requesting a doctor to prove their condition; those over away from their voting place are also excused by asking for a certificate at a police station near where they are. Belgian voters can vote in an embassy if they are abroad or can empower another voter to cast the vote in their name; the voter must give a "permission to vote" and carry a copy of the eID card and their own on the actual elections.
2004 European Parliament election in Luxembourg
The Luxembourg electoral system allows each voter to cast as many votes as there are
members to be elected. These figures show the number of votes cast for each party, 
not the number of voters who cast them. Voting at European Parliament elections is obligatory (as is the case with all other kinds of elections in the country).