Greens Senator Janet Rice with MP Alex Greenwich and Human Rights Law Centre lawyer Anna Brown outside the Law Courts in Sydney where they have lodged a case against the federal government regarding same-sex marriage. Credit:James Alcock Those typically include MPs (and Opposition Leader Bill Shorten is one), judges and victims of crime who do not want to appear on the roll for privacy reasons. The Parliamentary Library said there were 113,000 such voters as of 2016. Acting Special Minister of State Mathias Cormann, who earlier in the week was confident ballot papers would be sent to silent electors, released a statement on Friday saying that this remained the government's intention. "Our commitment is for all Australians on the electoral roll, including silent electors, to have the opportunity to have their say on whether or not the law should be changed to allow same-sex couples to marry," he said. "The ABS will make further announcements in relation to this as soon as arrangements have been finalised."

The AEC said it expected a record proportion of Australians would be enrolled to vote. Credit:Edwina Pickles AEC spokesman Evan Ekin-Smyth said: "The AEC is working with the ABS regarding this issue. Relevant advice will be provided when available." Meanwhile in the High Court, chief justice Susan Kiefel said the full court would hear an urgent challenge to the validity of the postal vote on September 5 and 6. The hearing is expected to take one-and-a-half days. Acting Special Minister of State Mathias Cormann Credit:Andrew Meares The court heard an injunction to stop the postal vote going ahead before the hearing was not required because the ABS has agreed not to take steps to conduct the poll before September 12.

Two challenges to the validity of the vote have been lodged - one headed by Tasmanian MP Andrew Wilkie and the other by national organisation Australian Marriage Equality. At a directions hearing in Sydney on Friday, the High Court heard there is a significant degree of overlap between the two cases. The Australian Marriage Equality challenge is confined to two legal issues about the validity of the manner in which the government authorised the expenditure of money to conduct the vote. NSW independent MP Alex Greenwich, the co-chair of AME, said: "Our legal challenge is a reminder to the government that it's time they did their job and voted for marriage equality, rather than wasting time and money." The $122 million for the survey was not authorised by an Act of Parliament but was provided to the ABS by way of an advance from Senator Cormann, who is also the Finance Minister, under the Appropriation Act. An advance to the Finance Minister may be made if there is an "urgent need" for the funds and it was "unforeseen".

An issue in the case will be whether the expenditure was "unforeseen". A directions hearing will be heard on August 16, which is expected to narrow the issues. The government was also seeking advice on Friday about whether a legal loophole in the postal survey would accidentally allow 16-year-olds to vote. A direction given by the Treasurer Scott Morrison to the ABS declared that anyone who made "a valid application for enrolment" on the roll before August 24 would be eligible to participate in the survey. People aged 16 and 17 can make a "claim for enrolment" but are not able to vote in elections. Senator Cormann late on Friday dismissed speculation the loophole would give 16-year-olds the vote. "The survey instruments will be sent to those who are on the roll; 16- and 17-year-olds are not on the roll," he said. Also on Friday, the Equality Campaign officially launched its bid for a "yes" vote, and signed up former ALP national secretary Tim Gartrell as campaign director.