The coupon is on the back cover in the address area right under the Dell return address. there are two boxes, one for customer number and the other is coupon code. they are clearly marked if they are on your catalog. I have seen people post similar messages here, and it seems some people get the codes but not everyone. It has to be a small biz catalog I think. As for the previous post about a minimum purchase, i don'e see any fine print to that effect. It reads:
Take $100 off your next Dell purchase by phone or online. Simply buy any of Dell's powerful and reliable desktops, notebooks, or networking and storage devices and you will save $100 off your total order. This offer may be combined with any other special offer or discount we are offering on the systems of your choice.
I have tested the coupon in the shopping cart on items like the Canon G2 and other peripherals and it seems to work on everything.
YMMV