Assuming you are a customer so you have a partner who can help you? You are starting to get into areas that are going to raise continual questions.
Question 1. What is the business reason for configuring the item model group to not allow negative inventory?
Question 2. Why are you not running the inventory close - it has to be run to push costs through, and you cannot be running a live system with financial negative inventory not set and never running the costing whilst using production unless you are in your first month of live!
Okay to answer your questions.
1. It means every item you use has the purchase invoice processed, AND I believe the inventory close is run - as you dont run it you never push the costs through, so unless the purchase invoice is processed before you use it, you have a serious processing issue/gap.
2. Open the production order and go to the Production BOM. Select the line and then stock - transactions. Then go to Stock and Cost explorer. Any open issues are not financially closed and need to be - this means the cost has not been invoiced of the original inbound entry. Your item model group setting means you have to clear this up before selling it.
3. The item model group financial negative inventory you have unchecked. This means if you purchase something before you sell it you must have received the invoice. The same is true of a manufactured item, but there are many components, so potentially many invoices that go into the finished product, all have to be updated and the inventory close run to update the finished product cost.
4. Run it, you cannot work without it running (unless you are standard costed).
5. Go to the item, find the item model group and go to the record. On the stock model fast tab the stock model tells you the costing method.
6. Do all of this on test.
7. Take training, if you have a valid maintenance agreement use customersource or DLP. There is no one book that tells you everything about a system this large.
Steve