I was going to write that we also only do pre-paid fundraisers and then I remembered our Kidstuff coupon books. We send a book out to every student and then they take orders and/or buy the book. If they don't want to do either, they just return the book. We get @98% of our books back by the due date and the other 2% take a couple of phone calls/notes but they are all paid for or back to us by the time we REALLY need them back.
Oh! and Market Day - people order that and then pay at the sale. Perhaps that's different because they can't pick up their order without paying.... But, regular fundraisers are pre-paid.
We may be in the minority here but we have to prepay for all fundraisers except our candy bar sale. Any orders turned in must be prepaid. I'm curious as to how much lower your sales were when you tried this?
We have had that problem also. We found that offering "pre-orders" only has taken away a lot of our sales. So we switched back to our previous practice, but only give to students whose parents have signed a responsibiltiy wavier for fundraising items before they go home. This way the responsibity is on the parents and its easier to file in court if that is what it comes down too. After the waivers went home we haven't had any more problems.