27 CFR 19.250: Inventory reserve account.

(a) The proprietor may establish an inventory reserve account for any eligible distilled spirits product by maintaining an inventory reserve record as prescribed by § 19.614. The effective tax rate applied to each removal or other disposition will be the effective tax rate recorded on the inventory reserve record from which the removal or other disposition is depleted. With an inventory reserve account, the proprietor will tax pay removals on a first-in first-out basis regardless of which lot of product is actually removed.

(b) If the appropriate TTB officer finds that the use of this procedure jeopardizes the revenue, or causes administrative difficulty, the proprietor upon notification from TTB must discontinue use of this procedure.