All coupons from daily deal websites eventually expire, so if you purchase a voucher, make sure you redeem it before the expiration date. Most sites offer a refund of sorts, but it typically comes only in the form of a credit for a future deal. If you do forget to redeem a voucher, many merchants accept the coupon at the value you paid, so you at least don't lose your initial investment.
Brendan McDermid/Reuters/File
Groupon Chief Executive Andrew Mason (L) prepares for the opening bell ceremony celebrating his company's IPO at the Nasdaq in New York in 2011. One tip for shoppers at daily deal sites: Look carefully for a deal's expiration date.