[ADD] finance: avatax tax calculation

closes odoo/documentation#9114

Signed-off-by: Timothy Kukulka (tiku) <tiku@odoo.com>

content/applications/finance/accounting/taxes/avatax.rst

@@ -1,3 +1,5 @@
+:show-content:
+
 ==================
 Avatax integration
 ==================
@@ -72,3 +74,9 @@ cross-reference data in Odoo and Avatax.
 
 .. seealso::
    - :doc:`fiscal_positions`
+   - :doc:`avatax/avatax_use`
+
+.. toctree::
+   :titlesonly:
+
+   avatax/avatax_use

content/applications/finance/accounting/taxes/avatax/avatax_use.rst

@@ -0,0 +1,102 @@
+==========
+AvaTax use
+==========
+
+AvaTax is a tax calculation software that can be integrated with Odoo in the United States and
+Canada. Once the :doc:`integration setup <../avatax>` is complete, the calculated tax is simple and
+automatic.
+
+Tax calculation
+===============
+
+Automatically calculate taxes on Odoo quotations and invoices with AvaTax by confirming the
+documents during the sales flow. Alternatively, calculate the taxes manually by clicking the
+:guilabel:`Compute taxes using Avatax` button while these documents are in draft mode.
+
+.. tip::
+   Clicking the :guilabel:`Compute taxes using Avatax` button recalculates taxes if any product
+   lines are edited on the invoice.
+
+.. image:: avatax_use/calculate-avatax.png
+   :align: center
+   :alt: Sales quotation with the confirm and compute taxes using AvaTax buttons highlighted.
+
+The tax calculation is triggered during the following :ref:`automatic trigger
+<avatax/automatic-triggers>` and :ref:`manual trigger <avatax/manual-triggers>` circumstances.
+
+.. _avatax/automatic-triggers:
+
+Automatic triggers
+------------------
+
+- When the sales rep sends the quote by email with :guilabel:`Send by email` button (pop-up).
+- When the customer views the online quote on the portal.
+- When a quote is confirmed and becomes a sales order.
+- When the customer views the invoice on the portal.
+- When a draft invoice is validated.
+- When the customer views the subscription in the portal.
+- When a subscription generates an invoice.
+- When the customer gets to the last screen of the eCommerce checkout.
+
+.. _avatax/manual-triggers:
+
+Manual triggers
+---------------
+
+- :guilabel:`Compute taxes using Avatax` button at the bottom of the quote.
+- :guilabel:`Compute taxes using Avatax` button at the top of the invoice.
+
+.. tip::
+   Use the :guilabel:`Avalara Partner Code` field that is available on customer records, quotations,
+   and invoices to cross-reference data in Odoo and AvaTax. This field is located under the
+   :menuselection:`Other info` tab of the sales order or quotation in the :guilabel:`Sales` section.
+
+   On the customer record, navigate to *Contacts app* and select a contact. Then open the
+   :guilabel:`Sales & Purchase` tab and the :guilabel:`Avalara Partner Code` under the
+   :guilabel:`Sales` section.
+
+.. important::
+   The :guilabel:`Automatic Tax Mapping (AvaTax)` fiscal position is also applied on those Odoo
+   documents, like subscriptions.
+
+.. seealso::
+   - :doc:`../fiscal_positions`
+
+AvaTax synchronization
+======================
+
+Synchronization occurs with AvaTax, when the *invoice* is created in Odoo. This means the sales tax
+is recorded with Avalara (AvaTax software developer).
+
+To do so, navigate to :menuselection:`Sales app --> Orders --> Quotations`. Select a quotation from
+the list.
+
+After confirming a quotation and validating the delivery, click :guilabel:`Create Invoice`. Indicate
+whether it is a :guilabel:`Regular invoice`, :guilabel:`Down payment (percentage)`, or
+:guilabel:`Down payment (fixed amount)`.
+
+Then click :guilabel:`Create and view invoice`. The recorded taxes can be seen in the
+:guilabel:`Journal Items` tab of the invoice. There will be different taxes depending on the
+location of the :guilabel:`Delivery Address`.
+
+.. image:: avatax_use/journal-items.png
+   :align: center
+   :alt: Journal items highlighted on a invoice in Odoo.
+
+Finally, press the :guilabel:`Confirm` button to complete the invoice and synchronize with the
+AvaTax portal.
+
+.. warning::
+   An invoice cannot be :guilabel:`Reset to draft` because this causes de-synchronization with the
+   AvaTax Portal. Instead, click :guilabel:`Add credit note` and state: `Sync with AvaTax Portal`.
+   See this documentation: :doc:`../../../accounting/customer_invoices/credit_notes`.
+
+Fixed price discounts
+=====================
+
+Add a fixed price discount to a valuable customer by click :guilabel:`Add a line` on the customer's
+invoice. Add the product discount and set the :guilabel:`Price` to either a positive or negative
+value. To recalculate the taxes, click :guilabel:`Compute taxes using Avatax`.
+
+.. tip::
+   Tax calculation can even be done on negative subtotals and credit notes.