Why can't some credit references be verified?

In working with credit card companies, I found that a lot of the time it could be as simple as the previous creditor never reported to any of the credit agencies. Another popular problem is that they don't "like" the type of reference provided. For instance, you have paid your car loan on time each month and it is reported but you don't carry any major credit cards. Often, especially when dealing with department store cards, they want to see someone else taking the risk first. Then there's always the possibility that the previous creditor was unwilling to answer questions regarding your accounts. Usually because they want to protect you. It's a vicious cycle really but there are several explanations. Hope this helps.