1) Detecting "Reduced Tax Rate":
* Identify product lines with a VAT rate that is neither 0% (exempt), 10% (minimum), nor 22% (basic). Any VAT rate outside these three should be considered "Reduced Tax Rate". 
2) Modifying XML Output:
* In the `<Totales>` section of the XML, include the total amount of VAT under the "Reduced Tax Rate" in the `<MntIVAOtra>` tag.
* Example: ```xml <MntIVAOtra>140</MntIVAOtra> ``` (where 140 corresponds to the VAT calculated at the reduced tax rate, e.g., 20%).
* For each product line using "Reduced Tax Rate," set the `<IndFact>` tag to `4`: ```xml <IndFact>4</IndFact> ```
    * Ensure the total amount reflects the base amount plus the VAT under "Reduced Tax Rate". 

3) Tax Grid for Configuration:
* Add a new tax grid called Sales Reduced VAT to be used for the tax configuration of the "Reduced Tax Rate."
* This will ensure proper reporting and consistency in tax declarations.
* The new tax grid should be selectable when configuring other taxes. 
Odoo Implementation Considerations:
* The tax computation logic in Odoo already supports defining taxes at different rates.
* Adapt the XML generation logic to check for product lines with a non-standard VAT rate and apply the necessary modifications. Ensure the final totals in the XML align with Odoo's computed tax amounts.

Task latam side: 1330
Task Adhoc side: 52999

Forward-Port-Of: odoo/enterprise#91392