diff --git a/addons/purchase/invoice.py b/addons/purchase/invoice.py
index b9d0b0ec05d..ddfa1484395 100644
--- a/addons/purchase/invoice.py
+++ b/addons/purchase/invoice.py
@@ -8,7 +8,8 @@ from openerp.tools.float_utils import float_compare
 class AccountInvoice(models.Model):
     _inherit = 'account.invoice'
 
-    purchase_id = fields.Many2one('purchase.order', string='Purchase Order', domain=[('invoice_status', '=', 'to invoice')])
+    purchase_id = fields.Many2one('purchase.order', string='Add Purchase Order', domain=[('invoice_status', '=', 'to invoice')],
+        help='Encoding help. When selected, the associated purchase order lines are added to the vendor bill. Several PO can be selected.')
 
     # Load all unsold PO lines
     @api.onchange('purchase_id')
@@ -61,7 +62,10 @@ class AccountInvoice(models.Model):
             if account:
                 data['account_id'] = account.id
             result.append(data)
+
+        self.invoice_line_ids = False # To avoid duplicates
         self.invoice_line_ids = result
+        self.purchase_id = False
         return {}
 
     @api.model
@@ -138,4 +142,7 @@ class AccountInvoice(models.Model):
 class AccountInvoiceLine(models.Model):
     """ Override AccountInvoice_line to add the link to the purchase order line it is related to"""
     _inherit = 'account.invoice.line'
+
     purchase_line_id = fields.Many2one('purchase.order.line', 'Purchase Order Line', ondelete='set null', select=True, readonly=True)
+    purchase_id = fields.Many2one('purchase.order', related='purchase_line_id.order_id', string='Purchase Order', store=False, readonly=True,
+        help='Associated Purchase Order. Filled in automatically when a PO is chosen on the vendor bill.')
diff --git a/addons/purchase/invoice_view.xml b/addons/purchase/invoice_view.xml
index 2717fe066e9..f09c08fce19 100644
--- a/addons/purchase/invoice_view.xml
+++ b/addons/purchase/invoice_view.xml
@@ -61,8 +61,20 @@
                  <field name="purchase_id" domain="[('invoice_status', '=', 'to invoice'), ('partner_id', 'child_of', partner_id)]" attrs="{'invisible': [('state', '&lt;&gt;', 'draft')]}" class="oe_edit_only"/>
             </field>
             <xpath expr="//field[@name='invoice_line_ids']/tree/field[@name='company_id']" position="after">
-                 <field name="purchase_line_id" invisible="1"/>
+                <field name="purchase_line_id" invisible="1"/>
+                <field name="purchase_id"/>
             </xpath>
         </field>
     </record>
+
+    <record id="view_invoice_line_form_inherit_purchase" model="ir.ui.view">
+        <field name="name">account.invoice.line.form.inherit.purchase</field>
+        <field name="model">account.invoice.line</field>
+        <field name="inherit_id" ref="account.view_invoice_line_form"/>
+        <field name="arch" type="xml">
+            <field name="account_id" position="before">
+                <field name="purchase_id"/>
+            </field>
+        </field>
+    </record>
 </odoo>