Schefter added that the deal voids after two years, essentially making it a two-year contract.
The Seahawks had roughly $427,000 in cap space prior to the deal, per Over the Cap.
Carson was widely considered to be one of the best running backs on the free-agent market.
In 2020, Carson appeared in 12 games, rushing for 681 yards and five touchdowns while adding a career-high 287 receiving yards and four touchdowns as he struggled with injuries. Through four seasons in the league, Carson has never appeared in all 16 games.
The team chose not to use the franchise tag on him, it was reported by NFL Network's Michael Giardi on Tuesday that the New England Patriots had been "in contact" with the Seahawks' seventh-round pick from 2017.
The Seahawks brought Ahkello Witherspoon in to serve as cornerback following the departure of Shaquill Griffin to the Jacksonville Jaguars in free agency.
They also reportedly signed tight end Gerald Everett and traded for guard Gabe Jackson. Jackson, with the re-signed center Ethan Pocic will function largely to please Russell Wilson, who has expressed his displeasure with the Seahawks offensive line.