Nicole Richie and her Good Charlotte rocker boyfriend, Joel Madden, are tying the wedding knot. Richie, 28, made the announcement Monday on The Late Show with David Letterman.

Their marital status has been shrouded in mystery since they first started dating in 2006, however, Nicole Richie has put the rumors to rest: She and Joel Madden are engaged.

A source tells UsMagazine. com, "Nicole and Joel are in the process of planning the wedding. She's very involved in every detail. She's thrilled".

The couple is expected to get married in the summer.

The 28-year-old made the admission during the Monday taping of the Late Show with David Letterman, announcing that after two children together she'll walk down the aisle with her rocker beau, reports E! Online.

In addition, it is reported that Richie and Madden started dating in December 2006 and have two children together namely Harlow, 2, and Sparrow, 5 months.

Last year, Richie told CNN's Larry King, "I think for both of us, we are going to do it because we want to, not because that's what you do. We're going to do it when the time's right".