The Australian Bureau of Statistics has received an estimated 11.9 million survey forms, which equates to approximately 75 per cent of voters.
"The ABS estimates it received an additional 300,000 forms in the last week," it said in its latest weekly update.
"With form scanning now well under way, the estimate is based on a count of forms scanned rather than earlier estimates that were based on the weight of the bulk containers of returned forms waiting to be scanned."
The Bureau has sent out forms to approximately 16 million eligible Australians to vote on whether same-sex couples should be allowed to marry in the $122 million survey.
Postal forms must be received by 6pm on November 7 to be included in the count.
The final results will be announced on November 15.