It seems you cannot change the valuation method once you have transactions against the item, even when the inventory is zero (at least in FP3). Can anyone confirm this? Any workaround you are aware of? What would I break if I updated the valuation method in whwmd210 using GTM?

I've never had trouble changing the valuation method with inventory on hand. I can understand that the valuation itself may not change, but the method should be changeable.

I just ran Change Valuation Method (whina1232m000) in our FP3 test company for one item with inventory and one item without. Both changes were successful. (The item with zero inventory had previous transactions.)

Needless to say, I would not recommend using GTM to change the method.

Are you getting an error message? What are the settings on the Selection, Inventory Value and Options tabs of whina1232m000?