LOS ANGELES (TheWrap.com) - Britney Spears has reached an agreement to serve as a judge on Simon Cowell's The X Factor -- and the payday is really something to sing about.

The Womanizer singer will collect US$15 million overall for the gig -- approximately US$13 million to judge music-industry aspirants alongside Cowell and record executive L.A. Reid, and the rest as a bonus for performing on the show, an individual with knowledge of the deal told TheWrap.