Inventory cost should not be adjusted. Inventory cost is what you actually pay for it.
Hello there, grace_yew,
You can directly go to the inventory item and edit the cost. Here's how:
Here's an article on how to use reports to see your sales and inventory status: https://community.intuit.com/articles/1790411.
If you have other concerns related to inventory, don't hesitate to post a question.
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