Recording of Lavigne's debut album, Let Go, finished in January 2002.
Lavigne released Let Go in June 2002 in the US, where it reached number two on the Billboard 200 albums chart.
It was only when Lavigne then went to Los Angeles in May 2001 and created two songs with The Matrix production team—including "Complicated", later released as her debut single—that the record company felt she had made a major breakthrough.
Lavigne worked further with The Matrix and also with singer-songwriter Cliff Magness.
Her breakthrough single, "Complicated", peaked at number 1 in many countries around the world, as did the album Let Go.
Her second studio album, Under My Skin, was released in May 2004 and was her first album to peak at number 1 on the US Billboard 200, eventually selling more than 10 million copies worldwide.
It peaked at number one in Australia, Canada, and the UK—this made Lavigne, at 17 years old, the youngest female soloist to have a number-one album on the UK Albums Chart at that time.
Lavigne's debut single, "Complicated", peaked at number one in Australia and number two in the US.
By this time, Lavigne had found that she fit in naturally with her hometown high school's skater clique, an image that carried through to her first album, but although she enjoyed skateboarding, school left her feeling insecure.
Ken Krongard, an A&R representative, invited Antonio "L.
A." Reid, then head of Arista Records, to Zizzo's Manhattan studio to hear Lavigne sing.
"Complicated" was one of the bestselling Canadian singles of 2002, and one of the decade's biggest hits in the US, Lavigne wrote most of the album's tracks with Canadian singer-songwriter Chantal Kreviazuk, and Kreviazuk's husband, Our Lady Peace front man Raine Maida, co-produced the album with Butch Walker and Don Gilmore.
Lavigne said that Under My Skin proved her credentials as a songwriter, saying that "each song comes from a personal experience of mine, and there are so much[sic] emotions in those songs".