Theresa Binge, 43, was reported missing days after disappearing from O'Shea's Royal Hotel in Goondiwindi, Queensland, on July 18, 2003.Â
Her body was found weeks later in a stormwater culvert beneath a rural road just across the border in NSW.
Police in the northern NSW town of Moree launched a murder investigation after the discovery but no charges have ever been laid over Ms Binge's death.
Detectives will travel to Moree on Tuesday to announce the $1 million reward alongside her daughter, Daylene Barlow.
The reward builds on a $100,000 offer announced in 2007 for information leading to an arrest and conviction for the crime.
A coronial inquiry that same year found Ms Binge was likely murdered by an unknown person.
Her family has never stopped searching for the truth and thousands of people follow a social media page that provides updates on the investigation.
The page continues to call for action, with the words "justice is due" featured in its bio.
Ms Binge was last seen wearing a horizontal striped black and yellow football jersey, silver track pants and white running shoes.
Anyone with information should contact police via Crime Stoppers.
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