Out British singer Sam Smith will reportedly donate a large portion of ticket sales from his upcoming Sydney show to the campaign for marriage equality in Australia.

The Australian government is spending an estimated $120 million on a postal survey which asks, “Do you support a change in the law to allow same-sex couples to marry?” Participation in the survey is non-compulsory and the results, expected November 15, are not binding.

Smith is scheduled to perform at Sydney's Opera House in January.

The Australian Marriage Equality campaign told the Sydney Morning Herald that Smith has donated a third of his profits ahead of his performance to maximize its impact.

(Related: Macklemore, Mary Lambert perform gay anthem Same Love at NRL grand final.)

“Sam knows all too well about the challenges faced by LGBTI Australians and his generosity towards them will help us achieve fairness and equality for all,” said Australian Marriage Equality co-chair Janine Middleton.

“Sam doesn't need to do this. He isn't Australian but he understands what it feels like to be in a relationship that isn't considered equal,” Middleton added. “Soon we hope to realize the equality he enjoys at home in the United Kingdom will soon be a reality here in Australia.”

(Related: Sam Smith urges Australia to “change for the better” as same-sex marriage vote begins.)