If a business doesn't have the exact inventory value at the time of filing its tax return, the business should estimate the value that it should have been as of the end of the month. If the inventory amount is later determined, an amended return should be filed. To comply with the applicable rules and regulations, the following month's inventory should be performed on the last day of the month.
For more information, see TENN. COMP. RULES & REGULATIONS 1320-4-2-.06(2)(d).
Reference: Rule 1320-4-2.pdf