You can edit your purchase (including quantity, billing information, or canceling your order) until midnight the day of the deal, or while the deal is still live.
To change your purchase, please sign into your account at Groupon.com. Once you are signed in, you will see your name at the top of the deal page. Scroll over your name and your account menu will drop down for you to access "My Groupons."
Once you're there, click on "edit purchase" next to the Groupon you purchased. On this page you'll be able to make changes to your order; you can change quantity, billing info, or cancel.
Dec 28, 2011