The band once featured Carol Heller (Guitar/Backing Vocals), formerly of Get the Girl, but has since been replaced. She was recorded in the demo version of the song "No It Isn't". The name Plus 44 is a reference to the international dialing code for the United Kingdom, where Hoppus and Barker first discussed the new project. On December 13th 2005, the band released a demo of the song No It Isn't. On September 1st 2006, they added a song called "Lycanthrope" to their official website. Also on September 7th, the (+44) Song "When Your Heart Stops Beating" was played on KROQ radio. On September 18th, an unedited version of the song was posted on the band's MySpace profile. As of September 21, 2006, the video is still being edited, however at a show in Hamburg, Mark announced that the video should be released on September 25.

Their debut album "When Your Heart Stops Beating" was released on November 14, 2006. Regarding the lyrical content of the album, Hoppus stated that "the +44 album is by far the most lyrically personal music I have ever written. The words are everything I have inside me put on a CD. This is the most personal album any of us have ever written. You want to know who we are, what we think, or how we feel? Listen to the +44 CD." The album refers to the break-up of blink-182, and "the ugly feelings that were left over afterwards," according to Hoppus. The song "No It Isn't", released on Tom Delonge's birthday, December 13, is primarily directed towards Delonge's departure from Blink-182.