[ADD] accounting: How to apply specific taxes by country, state or city?

https://docs.google.com/document/d/1eFgEV-0CMTU5R3eEIfSbAfy2NRkXWlhOra55Fzj5_MA/

accounting/others/taxes/application.rst

@@ -1,3 +1,131 @@
 =========================================================
-How to apply specific taxes by country, state or city?
+How to apply specific taxes by country, state or city ?
-=========================================================
+=========================================================
+
+In Odoo, the default tax to apply on a product/service is set on the
+**product form**. But, some customers may have specific tax rates because of
+their status (in some countries, construction companies are VAT exempts)
+or their location (customers in a different country, state and/or city
+may be subjected to another tax rate).
+
+In order to select the right tax to apply according to the customer or
+product, Odoo uses the concept of **fiscal positions**. If a customer has a
+specific fiscal position, the default tax may be replaced by another
+one. (as an example, construction companies have 0% instead of 21% in
+Belgium for construction related work).
+
+As an example, in Belgium, for the VAT tax, there are 3 fiscal positions
+that depend on on the country of the customer and some companies (like
+construction companies) benefit from a specific fiscal treatments:
+
+-  **Belgian companies:** with 21% VAT (default, on product form)
+
+-  **European companies:** with 0% VAT (intra-EU)
+
+-  **Other countries:** 0% (but a different tax since it uses different
+   accounts)
+
+-  **Construction companies:** with 0% VAT, only for construction companies
+   in Belgium
+
+Configuration
+=============
+
+Set the right taxes on your products
+------------------------------------
+
+The main taxes are automatically configured according to the chart of
+accounts of your country.
+
+But if you want to set a specific tax on a specific product, you can set
+the **sales and purchases taxes** on the **product form**, under the **Accounting
+tab**. These taxes are the default one (used when you sell to companies
+that are in the same country/state than you)
+
+.. image:: media/application05.png
+   :align: center
+
+.. tip::
+    If you work in a multi-company environment, the sales and 
+    purchase taxes may have a different value according to the 
+    company you work for. You can login into two different companies 
+    and change this field for each company.
+
+Defining Fiscal Positions
+-------------------------
+
+The main fiscal positions are automatically created according to the
+chart of accounts of your country. But you may have to create fiscal
+positions manually for specific use cases.
+
+To define fiscal positions, from the **Accounting** application, go to
+:menuselection:`Configuration --> Fiscal Positions`.
+
+Fiscal position is just a set of rules that maps default taxes (as defined on
+product form) into other taxes. In the screenshot below, european
+customers have a VAT of 0% instead of the default 15%, for both sales
+and purchases.
+
+.. image:: media/application02.png
+   :align: center
+
+.. note::
+    You can also map the **income / expense account** according to the fiscal
+    position. For example, in Belgium, revenues from sales are not posted in
+    the same account than revenues from sales in foreign countries.
+
+Apply fiscal positions automatically
+------------------------------------
+
+If you check the box **Detect Automatically**, the fiscal position will be
+applied automatically if the **Country**, **State**, **City** or even the 
+**Country Group** matches. You can also apply the fiscal position only 
+to companies having a valid **VAT number**.
+
+You can also set a target **Country/State/City**. The fiscal position will
+be applied if the destination address of the customer matches these
+criteria.
+
+.. image:: media/application04.png
+   :align: center
+
+Specific use cases
+------------------
+
+If, for some fiscal positions, you want to remove a tax, instead of
+replacing by another, just keep the **Tax to Apply** field empty.
+
+.. image:: media/application03.png
+   :align: center
+
+If, for some fiscal positions, you want to replace a tax by two other
+taxes, just create two lines having the same **Tax on Product**. You can
+also create one that is a grouping of two other taxes, depending on how
+you want to make them appear on the invoice.
+
+Using fiscal positions
+======================
+
+If you keep the field **Fiscal Position** empty on customers 
+:menuselection:`Accounting --> Sales --> Customers`, the fiscal position 
+is applied automatically on sales order, purchase orders, web orders and invoices.
+
+.. image:: media/application01.png
+   :align: center
+
+But, if you set the fiscal position, Odoo will use this specific fiscal
+position for this customer on orders (example: construction companies).
+In such a case, it’s recommended to set the fiscal position on the
+customer form. Odoo will automatically reuse this value for orders and
+invoices, without trying to auto-detect the fiscal position.
+
+If you set the fiscal position at the sale order or invoice level, it
+will only apply to this document only and not to future orders/invoices
+of the same customer.
+
+For eCommerce orders, the tax of the visitor’s cart will automatically
+update and apply the new tax after the visitor has logged in or filled
+in his shipping address.
+
+.. todo::
+    seealso to **How to define new taxes**