Each item code has to link to the GL Inventory Control Account Code. It is the control account.
When user post a purchase receipt, the double entry will be
Dr Inventory Cr Receipt Credit.
When User posts the AP invoice and match against the PO Goods receipt, the double entry will be
Dr Receipt Credit Cr Creditor Control.
When User posts the delivery order or AR invoice, the double entry will be
Dr COGS Cr Inventory
Dr Debtors Cr Sales
User has to made adjustment from the inventory control module and not directly from the General Ledger module.