Whenever you
purchase anything anywhere in
Taiwan and receive a printed
receipt, it has an eight
digit serial number printed on it. Every month, a few
lucky winners who get the selected numbers on a
receipt may pick up a substantial
jackpot, and there are lesser prizes too. The more you buy, the better your chances.
Of course, most jaded expatriates like myself toss out all those receipts and never bother. I've thrown out thousands of receipts and probably several million dollars, with my luck. But fans of the lotto file every receipt they get and sort them too, for easy comparison. This is sort of like the coupon clippers in America (coupons are rarely used in Taiwan). Many charities put boxes out in stores so you can donate your receipts.
I guess the idea is to encourage the sales tax. You get a receipt at the 7-Eleven or Chung Yo, but not at your local fan guan or breakfast stand--meaning they aren't charging you sales tax either.