Reed filed divorce papers in Los Angeles Superior Court on May 16, according to People magazine. The 25-year-old "Twilight" franchise star cited irreconcilable differences and is seeking to deny 29-year-old McDonald spousal support.
The couple announced their separation back in March.
In a joint statement, the estranged couple said they had been living separately for six months before the announcement "due to work obligations," but noted that they would continue to work on their debut album, "I'm Not Falling," despite the split.
Reed and McDonald, who was a contestant on season 10 of "American Idol," met at the premiere of the film "Red Riding Hood" in March 2011. They became engaged in June 2011 and, according to People magazine, the two wed in October 2011.