Jay Z is the newer, correct spelling of Jay-Z. According to a Pitchfork article, "Jay-Z is shedding some baggage in his post-Magna Carta Holy Grail life. According to Billboard editor Joe Levy, "Jay Z has dropped the hyphen from his name, according to his label." Billboard has since dropped the hyphen from articles mentioning Jay, SPIN points out. Jay's website is billed as "JAY Z's Life+Times". And "JAY Z" is how his music is listed on iTunes."
JAY Z on Last.fm.