From the US Mensa website:
  • This November and December, you can qualify and join Mensa in one easy step!  If you submit your qualifying test scores and your first year's membership dues before December 31, 2012, you'll pay only $84 — we'll review your test score for free and extend your membership through March 31, 2014. You'll automatically become a member upon qualifying, and you'll save money by having your test scores reviewed for free!