**Issue Description**:
Currently, the order in which taxes are applied can vary based on the sequence they are entered in the invoice's Taxes field. This inconsistency arises when the tax list is not manually adjusted, leading to each tax having an identical sequence value. As a result, their hierarchy within the `flatten_taxes_hierarchy` function is determined by their input order rather than a defined sequence, causing unpredictable tax calculations.
https://github.com/odoo/odoo/blob/56666f8f7858fcbcce466d2240135b35509d2d96/addons/account/models/account_tax.py#L611-L632
A tax sequence should be explicitly defined, and in cases where sequences are identical, organization by tax ID should be enforced.
**Steps to Reproduce**:
1. Navigate to the `Account` or `Invoice` application.
2. Go to `Configuration > Taxes`.
3. Create a new tax with the advanced option `Affect Base of Subsequent Taxes` and specify an amount.
4. Generate a new invoice and add a line item priced at 100.
5. Apply taxes in the `Taxes` column in the following order: 15% followed by the newly created tax, and note the total amount.
6. Repeat step 5, but reverse the order of the taxes.
7. Observe that the total amounts differ between the two sequences.
**Proposed Solution**:
To ensure that taxes are applied consistently regardless of input order, we will modify the `flatten_taxes_hierarchy` function to add sorting by id. If the sequences are identical, the sorting will depend only on the id, otherwise it will be based on the sequence. This setting ensures a predictable and logical process for applying taxes.
opw-3691765
closesodoo/odoo#156337
X-original-commit: 4afc5657a112a1466bc9bfe5ca6c4a64cbdb717e
Signed-off-by: Laurent Smet (las) <las@odoo.com>
Signed-off-by: Ilya Rudy (ilru) <ilru@odoo.com>
ilru-odoo
b238770e5a