[ADD] accounting: When should I use supplier bills or purchase receipts?

https://docs.google.com/document/d/1rb6yiFB6d4BU-lhH1eHyqq7q-9w2HaxT04vbehc6tcI/edit#heading=h.w8bu48g6z8cy

accounting/bank/reconciliation.rst

@@ -0,0 +1,9 @@
+===================
+Bank Reconciliation
+===================
+
+.. toctree::
+   :titlesonly:
+
+   setup/create_bank_account
+   setup/manage_cash_register

accounting/bank/reconciliation/use_cases.rst

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+=============================================
+Use cases in the bank reconciliation process?
+=============================================

accounting/bank/setup.rst

@@ -1,9 +1,8 @@
-===========
-Bank & Cash
-===========
+=====
+Setup
+=====
 
 .. toctree::
    :titlesonly:
 
-   setup/create_bank_account
-   setup/manage_cash_register
+   reconciliation/use_cases

accounting/payables/supplier_bills/bills_or_receipts.rst

@@ -1,3 +1,68 @@
 ======================================================
 When should I use supplier bills or purchase receipts?
 ======================================================
+
+Purchase receipts are different than vendor bills. Vendor bills are
+requests for payment. If I issue a Purchase Order my vendor will in most
+business cases send me a Vendor Bill. Depending on his invoice policy I
+then have a defined amount of time to pay the Bill. A Purchase receipts
+are confirmations of received paiements. They are my day-to-day ticket
+receipts.
+
+From an accounting point of view this makes a difference as a Vendor
+Bill will first credit a debt account before reconciling with the bank
+account. On the other hand we usually immediately pay the purchase
+receipts, which means no debt account is necessary.
+
+Moreover purchase receipts can have a different tax amount per product
+line, as vendors bills apply one taxe amount over the entire bill.
+
+If my company's bank account is used to pay for goods were only a
+purchase receipt are issued I should use the purchase receipts function
+in Odoo to handle them in accounting.
+
+Let's take the following example: we need to buy foreign tea for our
+customers from a local tea store that doesn't issue bills. We go every
+week buy 50 euros worth of tea and a teapot worth 20 euros. We pay with
+the company's bank account.
+
+Configuration
+=============
+
+To handle purchase receipts in Odoo one module and one app has to be
+installed. Go into the app module and install the accounting app.
+
+.. image:: ./media/bill01.png
+  :align: center
+
+Then, go in the search bar, delete the default module search, and search
+for "purchase". Install the **Sale & Purchase Vouchers** module.
+
+.. image:: ./media/bill02.png
+  :align: center
+
+Register a receipt 
+===================
+
+By installing the **Sale & Purchase Vouchers** I've made the new
+**Purchase Receipts** drop down menu visible in the accounting app.
+
+To import our 50 euros worth of tea purchase receipt, enter the
+accounting app, select :menuselection:`Purchases --> Purchase Receipts`.
+
+Create a new Purchase Receipt and fill in all the necessary information.
+Note that you have the choice in the Payment field between **Pay Later**
+or **Pay Now**. It's a significant difference as Pay Later, will generate
+a debt accounting entry whereas Pay Now will immediately credit the Bank
+account.
+
+In most cases you immediately pay, we will thus select the Pay Directly
+option. Add the products, the related account and the appropriate taxe.
+For the example we suppose the tea is a 12% taxe and the Tea Pott 21%.
+
+.. image:: ./media/bill03.png
+  :align: center
+
+Validate the Purchase Receipt to post it. Don't forget you need to
+:doc:`reconcile payments <../../bank/reconciliation/use_cases>` in order to completely close the transaction in your
+accounting.