In Odoo 18, once a Landed Cost has been validated and applied to products, it affects the Stock Valuation Layer  and the Accounting Entries.So deleting a validated landed cost is not directly possible from the user interface,it can be manually adjust the Landed Cost Amounts via reverse landed cost method.

Steps to Reverse a Landed Cost in Odoo 18

• Manually Adjust the Landed Cost Amounts:

1. Go to Inventory → Operations → Landed Costs.
2. Find the validated landed cost entry.
3. Instead of deleting, create a new landed cost entry(same as validated landed cost ) with a negative amount .

• Adjust the Accounting Entries :

1. Navigate to Accounting → Journal Entries.
2. Locate the journal entry related to the landed cost.
3. Create a reversing journal entry if required.

Regards,
Milu
Accurates