Is it compulsory to vote in a plebiscite?
Thanks for your question.
A plebiscite can be used to help decide a national question that does not affect the Australian Constitution. When Australia has held plebiscites in the past, it has not been compulsory to vote. However, there are no specific rules for how a plebiscite should be conducted. If another plebiscite was held, the Australian Parliament would decide how it would be conducted, including whether it was compulsory to vote.
People voting

Australian Electoral Commission
Description
Three people are in a polling place completing their ballot papers in cardboard voting booths. Each voter is separated in their own booth to ensure their vote is secret.
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