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.