Only one item? That's all? How much money are you talking about here? A $5 item? A $5,000 dollar item? Depending on the amount, there may be no need to amend anything for just one measly item of inventory.
I have filed a State amended tax return for 2017
How did you change the inventory count on the state return, without changing it on the federal return first? Did you amend via some method other than TurboTax maybe?
