The Court sets out the gravamen of the two side's arguments as follows:
The government seizes upon the plain meaning of the word "payment," arguing that there can be no overpayment until there has actually been a payment—and there was no payment until Ford requested that its deposits be converted into tax payments. Prior to that point, Ford's remittances were, at its own request, treated as deposits in the nature of a cash bond and Ford could have requested their return at any time. As Revenue Procedure 84-58 § 2.03 clearly states, "[a] deposit in the nature of a cash bond is not a payment of tax." Accordingly, the government argues that it does not owe Ford interest from the date of the original remittances because they were indisputably made only as deposits, not as payments of any tax obligation.
But, wait, this taxpayer argued.
Ford counters that the "most appropriate starting point" is not § 6611, but rather § 6601, the provision that governs underpayment interest. First, Ford contends that these two sections should be interpreted symmetrically because they both use very similar language, compare § 6601 ("date paid"), with § 6611 ("date of the overpayment"), and both deal with the accrual of interest on tax payments. Second, Ford notes that under § 6601(a), only a "payment" stops the accrual of underpayment interest against a taxpayer, and since a deposit in the form of a cash bond stops the accrual of interest from the date it is remitted, Rev. Proc. 84-58 § 5.01, that deposit must be considered a payment under § 6601(a). And because a deposit is treated as a payment for underpayment interest purposes under § 6601, it should also be considered a payment for overpayment interest purposes under § 6611. In other words, if a mere deposit stops the accrual of underpayment interest, then a mere deposit must also start the accrual of overpayment interest.