I have the new Iris 3 tier project case holder and it works perfectly for my monthly bills. I have one labeled for my monthly household bills, one for credit card receipts and one for bills related to my beach house.
As I process my daily mail and receipts, I place each piece in the appropriate project case. When the time comes to process them, I pull the project case out and everything I need is right there together. The case can travel with me to another part of the house or in the car if I am working on it while I travel. It saves me time as I no longer have to search for all related items when I am paying bills. And, it keeps me organized to readily find whatever bill or receipt I am looking for.