[ADD] How to re-invoice expenses to your customer.

https://docs.google.com/document/d/1_6VclRWfESHfvNPZI32q5ANFi2C7cCTwkLXpbGTz6B8/edit#heading=h.96noud6ebpqt

sales/invoicing/services/reinvoice.rst

@@ -1,3 +1,188 @@
 =============================================
 How to re-invoice expenses to your customers?
-=============================================
+=============================================
+
+It often happens that your employees have to spend their personal money
+while working on a project for your client. Let's take the example of an
+employee paying a parking spot for a meeting with your client. As a
+company, you would like to be able to invoice that expense to your
+client.
+
+In this documentation we will see two use cases. The first, very basic,
+consists of invoicing a simple expense to your client like you would do
+for a product. The second, more advanced, will consist of invoicing
+expenses entered in your expense system by your employees directly to
+your customer.
+
+Use case 1: Simple expense invoicing
+====================================
+
+Let's take the following example. You are working on a promotion
+campaign for one of your customers (``Agrolait``) and you have to print a
+lot of copies. Those copies are an expense for your company and you
+would like to invoice them.
+
+Configuration
+-------------
+
+In order to sell services and to send invoices, you need to install the
+**Sales** application, from the **Apps** icon.
+
+.. image:: media/reinvoice01.png
+    :align: center
+
+Create product to be expensed
+-----------------------------
+
+You will need now to create a product called ``Copies``.
+
+From your **Sales** module, go to :menuselection:`Sales --> Products` 
+and create a product as follows:
+
+-   **Product type**: consumable
+
+-   **Invoicing policy**: on delivered quantities (you will manually
+    set the quantities to invoice on the sale order)
+
+.. image:: media/reinvoice02.png
+    :align: center
+
+Create a sale order
+-------------------
+
+Now that your product is correctly set up, you can create a sale order
+for that product (from the menu :menuselection:`Sales --> Sales Orders`) 
+with the ordered quantities set to 0. 
+Click on **Confirm the Sale** to create the sale
+order. You will be able then to manually change the delivered quantities
+on the sale order to reinvoice the copies to your customer.
+
+.. image:: media/reinvoice03.png
+    :align: center
+
+Invoice expense to your client
+------------------------------
+
+At the end of the month, you have printed ``1000`` copies on behalf of your
+client and you want to re-invoice them. From the related sale order,
+click on **Delivered Quantities**, manually enter the correct amount of
+copies and click on **Save**. Your order line will turn blue, meaning that
+it is ready to be invoiced. Click on **Create invoice**.
+
+.. note::
+    The total amount on your sale order will be of 0 as it is computed on 
+    the ordered quantities. It is your invoice which will compute the 
+    correct amount due by your customer.
+
+The invoice generated is in draft, so you can always control the
+quantities and change the amount if needed. You will notice that the
+amount to be invoiced is based here on the delivered quantities.
+
+.. image:: media/reinvoice04.png
+    :align: center
+
+Click on validate to issue the payment to your customer.
+
+Use case 2: Invoice expenses via the expense module
+===================================================
+
+To illustrate this case, let's imagine that your company sells some
+consultancy service to your customer ``Agrolait`` and both parties agreed
+that the distance covered by your consultant will be re-invoiced at
+cost.
+
+Configuration
+-------------
+
+Here, you will need to install two more modules:
+
+-   Expense Tracker
+
+-   Accounting, where you will need to activate the analytic accounting
+    from the settings
+
+.. image:: media/reinvoice05.png
+    :align: center
+
+Create a product to be expensed
+-------------------------------
+
+You will now need to create a product called ``Kilometers``.
+
+From your **Sales** module, go to :menuselection:`Sales --> Products` 
+and create a product as follows:
+
+-   Product can be expensed
+
+-   Product type: Service
+
+-   Invoicing policy: invoice based on time and material
+
+-   Expense invoicing policy: At cost
+
+-   Track service: manually set quantities on order
+
+.. image:: media/reinvoice06.png
+    :align: center
+
+Create a sales order
+--------------------
+
+Still from the Sales module, go to :menuselection:`Sales --> Sales Orders` 
+and add your product **Consultancy** on the order line.
+
+.. tip::
+    If your product doesn't exist yet, you can configure it on the fly 
+    from the SO. Just type the name on the **product** field and click 
+    on **Create and edit** to configure it.
+
+Depending on your product configuration, an **Analytic Account** may have
+been generated automatically. If not, you can easily create one in order
+to link your expenses to the sale order. Do not forget to confirm the
+sale order.
+
+.. image:: media/reinvoice07.png
+    :align: center
+
+.. note::
+    Refer to the documentation :doc:`../../../accounting/others/analytic/usage` 
+    to learn more about that concept.
+
+Create expense and link it to SO
+--------------------------------
+
+Let's assume that your consultant covered ``1.000km`` in October as part
+of his consultancy project. We will create a expense for it and link
+it to the related sales order thanks to the analytic account.
+
+Go to the **Expenses** module and click on **Create**. Record your expense
+as follows:
+
+-   **Expense description**: Kilometers October 2015
+
+-   **Product**: Kilometers
+
+-   **Quantity**: 1.000
+
+-   **Analytic account**: SO0019 - Agrolait
+
+.. image:: media/reinvoice08.png
+    :align: center
+
+Click on **Submit to manager**. As soon as the expense has been validated
+and posted to the journal entries, a new line corresponding to the
+expense will automatically be generated on the sale order.
+
+Invoice expense to your client
+------------------------------
+
+You can now invoice the invoiceable lines to your customer.
+
+.. image:: media/reinvoice09.png
+    :align: center
+
+.. seealso::
+    * :doc:`support`
+    * :doc:`time_materials`
+    * :doc:`milestones`
+    * :doc:`../products/delivery`