Payne's deal with the defending champions comes with a partial guarantee in the first season, Charania adds.
The 24-year-old opened the 2018-19 campaign with the Chicago Bulls but was waived by the club in January. He then signed a pair of 10-day deals with the Cleveland Cavaliers. He averaged 6.3 points, 2.7 assists, and 1.8 rebounds in 40 games last season.
Payne was drafted 14th overall by the Oklahoma City Thunder in 2015. He played three games with the Dallas Mavericks' summer league squad earlier this month, averaging 20 points, five rebounds, and four assists.
The Raptors have made a number of minor additions since losing Danny Green and marquee star Kawhi Leonard to free agency. The Canadian side has also signed veteran forwards Stanley Johnson and Rondae Hollis-Jefferson this summer, as well as undrafted point guard Terence Davis. Patrick McCaw was also re-signed by the team on a two-year contract.