It seems that you have switching to the Anglo-Saxon accounting method in Odoo requires more than just setting it in the developer mode. You also need to configure the relevant accounts, products, and journal entries. Here are the steps to configure Anglo-Saxon accounting in Odoo 16:

Enable the Anglo-Saxon accounting method in the Accounting settings by going to Settings > Configuration > Accounting and selecting Anglo-Saxon Accounting under the Accounting Features section.

Create an Anglo-Saxon account for tracking the cost of goods sold. To do this, go to Accounting > Configuration > Accounts and create a new account with an account type of Stock Valuation Account and set the Use Anglo-Saxon Accounting checkbox to True.

Set the Stock Input Account for each product to the appropriate account. To do this, go to Inventory > Configuration > Products and edit each product. In the Inventory tab, set the Stock Input Account to the appropriate account.

Create a journal entry for the purchase of goods. Go to Accounting > Journal Entries and create a new journal entry. Debit the Stock Input Account and credit the Vendor account. Set the Anglo-Saxon checkbox to True.

When you sell a product, create a delivery order for the product. This will create a move record that will be used to generate the accounting entries for the sale.

After the delivery order is created, confirm it to create the move. This will generate the accounting entries for the sale. Debit the Customer account and credit the Stock Valuation Account.

By following these steps, you should be able to properly configure Anglo-Saxon accounting in Odoo 16.

Thanks! I will try.