[ADD] Accounting: new page about intrastat

Task-id 2721400

closes odoo/documentation#1475

X-original-commit: aa7a78331d
Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>

content/applications/finance/accounting/reporting/declarations.rst

@@ -7,4 +7,5 @@ Declarations
 .. toctree::
    :titlesonly:
 
-   declarations/tax_returns
+   declarations/tax_returns
+   declarations/intrastat

content/applications/finance/accounting/reporting/declarations/intrastat.rst

@@ -0,0 +1,28 @@
+=========
+Intrastat
+=========
+
+**Intrastat** is the system for data collection and statistic production of goods traded among the
+EU Member States. Organizations whose annual trade surpasses a certain threshold must provide data
+about the goods traded with other EU countries.
+
+.. seealso::
+   - `Eurostat Statistics Explained - Glossary: Intrastat
+     <https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Intrastat>`_
+
+.. note::
+   As of January 1, 2022, the reporting requirements have changed. One main modification concerns
+   the transaction codes which are now switching to a 2-digits format. All transactions recorded
+   after this date have to follow the new system’s rules.
+
+Configuration
+=============
+
+Go to :menuselection:`Accounting --> Settings --> Customer Invoices`, then enable **Intrastat** and
+*Save*. Once the Intrastat has been activated you are able to choose the **Default incoterm**.
+
+.. important::
+   If you created your Odoo database prior to **January 13, 2022**, please :ref:`upgrade
+   <general/upgrade>` the ``account_intrastat`` module to add the new transaction codes and
+   :ref:`install <general/install>` the ``account_invoice_expiry`` module to archive the old codes.
+