Having worked with Brian on several 3115s for my clients, I believe that the answer is no, you don't say that you are changing to cash method when you are already on the cash method. You are not changing your overall method of accounting. You are changing the accounting treatment of a specific item.
Can you call the auditor and ask him for the change number? He won't know, but perhaps he will know who to ask.
Some links, perhaps helpful, perhaps not. There must be some instruction on how to do this somewhere.
https://www.irs.gov/irm/part4/irm_04-011-006See (5)
A change in the characterization of an item may constitute a change in method of accounting if the change has the effect of shifting income from one period to another. For example, a change from treating an item as income to treating the item as a deposit is a change in method of accounting. See Rev. Proc. 91-31: Diebold, Inc. v. United States, 16 Cl. 193 aff'd. 891 F.2d 1579 (Fed. Cir. 1989) cert. denied 498 U.S. 823 (1990) (inventory to capital asset); Pacific Enterprises v. Commissioner, 101 T.C. 1 (1993) ("working gas" (inventory) to "cushion gas" (capital asset)); Humphrey, Farrington & McClain v. Commissioner, T.C. Memo. 2013-23 (advanced litigation expenses from deductible business expense to loans).
This article says that RP 91-31 provides an automatic procedure for making the change.
https://www.thetaxadviser.com/issues/20 ... hange.htmlBut Brian’s post seems to indicate that the RP is not necessarily helpful. Have you taken a look at it?