[ADD] accounting: add new doc about tax/vat returns (#606)

accounting/fiscality/taxes.rst

@@ -12,4 +12,5 @@ Taxes
    taxes/tax_included
    taxes/retention
    taxes/B2B_B2C
-   taxes/cash_basis_taxes
+   taxes/cash_basis_taxes
+   taxes/tax_returns

accounting/fiscality/taxes/tax_returns.rst

@@ -0,0 +1,122 @@
+============================
+Tax Return (VAT Declaration)
+============================
+
+Companies that are registered for **VAT (Value Added Tax)** must file a **Tax return** on a monthly
+or quarterly basis, depending on their turnover and the regulation of the country in which they are
+registered. A Tax return - or VAT return - gives the tax authorities information about the taxable
+transactions made by the company, the *output tax* it has charged its customers, and the *input tax*
+its vendors have charged it. Based on these values, the company can calculate the tax amount they
+have to pay or be refunded.
+
+.. note::
+   You can find information about VAT and its mechanism on `this page from the European Commission
+   <https://ec.europa.eu/taxation_customs/business/vat/what-is-vat_en>`_.
+
+.. todo:: add doc about intracom listing
+
+Prerequisites
+=============
+
+Tax Return Periodicity
+----------------------
+
+The configuration of the **Tax Return Periodicity** allows Odoo Accounting to compute your Tax
+Return correctly and also to send you a reminder to never miss a tax return deadline.
+
+To do so, go to :menuselection:`Accounting --> Configuration --> Settings --> Fiscal Periods`,
+and go to the **Tax Return Periodicity** section.
+
+- **Periodicity**: define here whether you file your tax return each month or every three months.
+- **Reminder**: define when Odoo should remind you to file your tax return.
+- **Journal**: select the journal in which to record the tax return.
+
+.. image:: media/tax_return_periodicity.png
+   :align: center
+   :alt: Configure how often tax returns have to be made in Odoo Accounting
+
+.. note::
+   This is usually configured during the :doc:`app's initial set up
+   <../../overview/getting_started/setup>`.
+
+Tax Grids
+---------
+
+Odoo generates Tax Reports based on the **Tax Grids** settings that are configured on your taxes.
+Therefore, it is crucial to make sure that all the recorded transactions use the right taxes. You
+can see on each Journal Item which Tax Grid is used for that transaction.
+
+.. image:: media/tax_return_grids.png
+   :align: center
+   :alt: see which tax grids are used to record transactions in Odoo Accounting
+
+To configure your taxes' Tax Grids, go to :menuselection:`Accounting --> Configuration --> Taxes`,
+and open the tax you want to modify. There, you can edit your tax settings, along with the tax
+grids that are used to record invoices or credit notes.
+
+.. image:: media/tax_return_taxes.png
+   :align: center
+   :alt: Configure taxes and their tax grids in Odoo Accounting
+
+.. note::
+   Taxes and reports are usually already pre-configured: a *Fiscal Localization Package* is
+   installed according to the country you select at the creation of your database.
+
+.. _tax_return_lock:
+
+Close a tax period
+==================
+
+Tax Lock Date
+-------------
+
+Any new transaction which accounting date is prior to the **Tax Lock Date** has its tax values moved
+to the next open tax period. This is useful to make sure that no change can be made to a report once
+its period is closed.
+
+Therefore, we recommend locking your tax date before working on your *Closing Journal Entry*. This
+way, other users can't modify or add transactions that would have an impact on the Closing Journal
+Entry, which helps you avoid some tax declaration errors.
+
+To check the current **Tax Lock Date**, or to edit it, go to :menuselection:`Accounting -->
+Accounting --> Lock Dates`.
+
+.. image:: media/tax_return_lock.png
+   :align: center
+   :alt: Lock your tax for a specific period in Odoo Acounting
+
+Tax Report
+----------
+
+Once all the transactions involving taxes have been posted for the period you want to report, open
+your **Tax Report**.
+
+To do so, go to :menuselection:`Accounting --> Reporting --> Tax Report`. You can also click
+on *TAX Report* from your *Accounting Overview*.
+
+Make sure to select the right period you want to declare by using the date filter. You can see an
+overview of your tax report. Then, click on the button *Closing Journal Entry*.
+
+.. image:: media/tax_return_closing.png
+   :align: center
+   :alt: Select the period for the tax return and create a closing journal entry in Odoo Accounting
+
+After having reviewed the generated Journal Entry, click on *Post*. In addition to posting the entry,
+Odoo automatically creates a PDF file with the **Tax Report** that you can download from the chatter
+and preview on the right column. It includes all the values to report to the tax authorities, along
+with the amount you have to pay or be refunded.
+
+.. image:: media/tax_return_report.png
+   :align: center
+   :alt: download the PDF with your Tax Report in Odoo Accounting
+
+.. note::
+   If you forgot to :ref:`lock your tax date <tax_return_lock>` before clicking on *Closing Journal
+   Entry*, then Odoo automatically locks your fiscal period on the same date as the Accounting Date
+   of your entry. This automatic lock happens when you click on *Post*. This safety mechanism can
+   prevent some fiscal errors, but it is advised to lock your tax date manually before, as described
+   above.
+
+.. seealso::
+   * :doc:`create`
+   * :doc:`../../overview/getting_started/setup`