- Install Accounting, Point of Sales
- Go to Accounting > Configuration > Taxes
- Create 2 taxes (e.g. Tax 15% and Tax 21%)
- Go to Accounting > Configuration > Fiscal Positions
- Create a new Fiscal Postion with the following line for Tax Mapping:
  * Tax on Product: Tax 21%
  * Tax to Apply: Tax 15%
- Go to Point of Sale > Products > Products
- Create a new Product (e.g. Test Product) with "Tax 15%" and "Tax 21%" in Customer Taxes
- Go to Point of Sales and configure a POS:
  * Activate "Fiscal Position per Order" and choose the created Fiscal Position
  * Add Bank as Payment Method
- Start a POS session
- Search "Test Product" and add it
- Click on Tax button and select the created Fiscal Position
- Proceed to payment
- Choose Bank and validate
- Exit the POS session
- Click on "CLOSE" and "VALIDATE CLOSING & POST ENTRIES"
An error message appeared with the following message: "Cannot create unbalanced journal entry"

When closing and posting entries, an account move and account move lines are created from the session orders.
For each order lines, taxes are computed from taxes on product and fiscal position of the order.
In this case, the product has 2 taxes applied (Tax 15% and Tax 21%).
Due to the chosen Fiscal Position, the Tax 15% is applied instead of Tax 21%.
For the order line, Tax 15% is applied 2 times.
But during the account move lines generation, the original Tax 15% and the converted Tax 15% are merged together,
because they represent the same tax (same model id).
So the Tax 15% is only applied once, which results on unbalanced amounts during reconciliation.

In Sales, for the same case, the tax is only applied once.
To stay consistent with Sales behavior, the tax will also be applied once in Point of Sale.

opw-2278826

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




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Forward-Port-Of: odoo/odoo#53549