The body overseeing the postal survey on same-sex marriage is working with online sales sites to take down listings of those trying to sell their ballots.
Deputy Australian Statistician Jonathon Palmer says some auction items have been blocked before they've gone online.
He estimates the number is less than 30 and says others have been removed promptly.
"It seems everyday or two someone has a crack at listing a form," he told ABC radio on Wednesday, thanking eBay and Gumtree for their co-operation.
"I think it's a bit of a joke frankly."
