It is time that the billions of dollars of money and bank account balances held by debtors be made available as security in a manner that is commercially practical. The rules governing the perfection of security interests in money and deposit accounts need to be reformed to allow perfection by filing. This article builds a case for the proposed revisions by addressing the vexing question “what is money.” A brief history, especially drawing upon the history of the UCC, of answers to this question is presented. Various policy rationales are explored including an examination of the different forms of payment utilized in the payment system. After demonstrating that permitting filing of security interests in money and deposit accounts will lower costs for some debtors as well as promote the policy goals of avoiding hidden property interests, simplicity, improvement of the complicated law of proceeds of collateral and comparable treatment of different types of debtors, the argument turns to the international context. Contrasting the US approach to the fixed and floating charge regime of the United Kingdom, an argument is made that the current proposal is consistent with harmonizing the treatment of different types of lenders to that in the UK and other UK based legal systems.