The provincial revenue agency recently filed close to 1,500 charges and is seeking at least $211 million in fines from companies in the goldsmithing and jewelry businesses.
The fraud charges involve wholesaler Carmen International of Montreal, three of its administrators, and eight jewelry stores and their administrators.
Along with hefty fines, the 11 suspects could face jail time.
Revenue Quebec spokesman Stephane Dion said Friday that investigations began a few years ago and uncovered a phoney billing system.
"We think it's about the biggest (ever)," Dion said.
"An operation like this is really major."
He said the alleged scheme involved the repeated use of false bills to obtain undeserved credits and tax refunds.
He said the accused were engaged "in an artificial commercial activity" that involved transforming pure gold to scrap gold, which was then shipped off to be recycled as pure gold. Pure gold is not taxed and scrap gold is taxable.
The charges were laid two years after warrants were carried out against Carmen International and its administrators.
The Quebec government agency also seized vehicles, buildings and bank accounts in 2011.
But the company then undertook legal action, alleging that Revenue Quebec had caused irreparable damage to the firm and had used illegal procedures.
That case is still before the courts.
The Canadian Press attempted to contact Carmen International on Friday by phone, but there was no answer.
Revenue Quebec said in a news release that its proof is based on 20,000 pages of documents and the testimony of informants.
The alleged activities took place between March 2006 and July 2010. Dion said he expected the accused to appear in court this fall.