Recently, I bought a new car and traded in my old car. When I bought my old car used in 2003, the Carfax report showed no major accidents, but when I went to trade it for a new car in 2008, the Carfax report, run by the dealer, indicated there was a major accident with the car before I bought it.
As a result, I received $2,500 less than the trade in value. I almost gave them my car. Carfax cannot be relied upon to give accurate information. Never, never, never pay them for a report.
If you want a report ask the dealer for one and then be sure to have the car inspected by an independent mechanic. Don't trust Carfax!