Switzerland employs mandatory referendums.
This type of referendum is utilized after an item has been passed by parliament and is then put to a vote. In contrast, an optional referendum is only held after a certain number of citizens or cantons request it.
At the federal level, Article 140, paragraph 1 of the Federal Constitution mandates compulsory voting on revisions to the Federal Constitution, the collective security organization membership (e.g., NATO), supranational communities (e.g., the EU), federal laws that lack a constitutional basis and are valid for more than a year (an emergency procedure). Article 140 paragraph 2 of the Federal Constitution mandates that only the people vote on certain matters, primarily as a component of the procedure for the comprehensive revision of the Federal Constitution.
At the cantonal level, each federated state's constitution regulates which matters necessitate a mandatory referendum. Consequently, there exist various scenarios. Nonetheless, all cantons must subject the revision of their constitution to a mandatory referendum (article 51). Some states also subject all state laws to a compulsory referendum, as well as any expense that exceeds a certain amount (referred to as a "financial" referendum).