The commercial network has been the FTA provider throughout the current $241 million TV deal, which includes full live coverage through Fox Sports, and a mix of live and delayed coverage on Ten.
With that deal up at the end of this year, there's been significant speculation for several months that Ten owners ViacomCBS weren't interested in an extension.
That speculation intensified when former Supercars series commentator Matt White left the Head of Sport role at Ten.
According to the Australian Financial Review the split between 10 and Supercars is now official.
"Network 10 will not renew its contract with the Virgin Australia Supercars Championship, which expires at the end of this year," Network 10 director of sport production Adam Cush told the AFR.
"Network 10 has enjoyed a great relationship with the Virgin Australia Supercars Championship over the past six years and it’s been a privilege to bring our audiences world-class racing.
"We look forward to finishing on a high with the 2020 Bathurst 1000 in October. We wish the drivers, crews and all those behind the scenes the very best for the 2021 season."
The final line of the quote suggests October's Bathurst 1000 will be Ten's final round, which would mean no live FTA coverage of the Sydney Motorsport Park finale in December.
Seven West Media, now headed by former Supercars CEO James Warburton, is expected to take over as the FTA provider in the new broadcast deal, which once again will be centred around live coverage through Fox Sports.
Seven was the Supercars broadcaster between 2007 and 2014, and is already set to return to the motorsport space with TCR Australia and S5000 coverage this season.