diff --git a/modules/purchase/purchase.py b/modules/purchase/purchase.py
index 4f9cd0f..39b356a 100755
--- a/modules/purchase/purchase.py
+++ b/modules/purchase/purchase.py
@@ -1017,6 +1017,9 @@ class Purchase(
                 logger.info("PROCESS_INVOICE:%s",action)
                 invoice = purchase.create_invoice(lots,action)
                 if not invoice:
+                    logger.info(
+                        "PROCESS_INVOICE_NO_INVOICE: purchase=%s action=%s",
+                        getattr(purchase, 'id', None), action)
                     continue
                 if action == 'prov':
                     invoice.reference = 'Provisional'
@@ -1028,6 +1031,7 @@ class Purchase(
                 
             if invoices:
                 cls._save_invoice(invoices,prepayment)
+        return invoices
 
     @classmethod
     def _save_invoice(cls, invoices,prepayment=None):
diff --git a/modules/purchase_trade/fee.py b/modules/purchase_trade/fee.py
index 4ae6f3d..90f107a 100755
--- a/modules/purchase_trade/fee.py
+++ b/modules/purchase_trade/fee.py
@@ -107,8 +107,9 @@ class Fee(ModelSQL,ModelView):
         ('invoiced', 'Invoiced'),
         ], string='State', readonly=True)
 
-    fee_landed_cost = fields.Function(fields.Boolean("Inventory"),'get_landed_status')
-    inv = fields.Function(fields.Many2One('account.invoice',"Invoice"),'get_invoice')
+    fee_landed_cost = fields.Function(fields.Boolean("Inventory"),'get_landed_status')
+    inv = fields.Function(fields.Many2One('account.invoice',"Invoice"),'get_invoice')
+    dn_cn = fields.Many2One('account.invoice', "DN/CN", readonly=True)
 
     weight_type = fields.Selection([
         ('net', 'Net'),
@@ -371,6 +372,7 @@ class Fee(ModelSQL,ModelView):
         Warning = Pool().get('res.user.warning')
         fees_to_invoice = []
         for fee in fees:
+            was_invoiced = fee.state == 'invoiced'
             if fee.state == 'invoiced':
                 warning_name = Warning.format(
                     "Fee already invoiced", [fee])
@@ -385,7 +387,28 @@ class Fee(ModelSQL,ModelView):
             if fee.purchase:
                 fl = FeeLots.search([('fee','=',fee.id)])
                 logger.info("PROCESS_FROM_FEE:%s",fl)
-                Purchase._process_invoice([fee.purchase],[e.lot for e in fl],'service')
+                fee.adjust_purchase_values()
+                invoices = Purchase._process_invoice(
+                    [fee.purchase], [e.lot for e in fl], 'service')
+                invoice = invoices.get(fee.purchase) if invoices else None
+                logger.info(
+                    "PROCESS_FROM_FEE_RESULT: fee=%s purchase=%s invoice=%s "
+                    "was_invoiced=%s",
+                    getattr(fee, 'id', None), getattr(fee.purchase, 'id', None),
+                    getattr(invoice, 'id', None), was_invoiced)
+                if not invoice:
+                    if was_invoiced:
+                        raise UserError(
+                            "No debit note or credit note was created for "
+                            "fee %s. The current fee values may be identical "
+                            "to the last invoiced values." % getattr(
+                                fee, 'id', None))
+                    raise UserError(
+                        "No invoice was created for fee %s. Please check "
+                        "that the fee has linked lots and invoiceable values."
+                        % getattr(fee, 'id', None))
+                if was_invoiced:
+                    cls.write([fee], {'dn_cn': invoice.id})
                 fees_to_invoice.append(fee)
             else:
                 raise UserError(
@@ -434,9 +457,9 @@ class Fee(ModelSQL,ModelView):
             ('quantity', '>', 0),
             ('invoice.state', '!=', 'cancelled'),
             ], order=[
-            ('invoice.invoice_date', 'DESC'),
-            ('invoice.id', 'DESC'),
-            ('id', 'DESC'),
+            ('invoice.invoice_date', 'ASC'),
+            ('invoice.id', 'ASC'),
+            ('id', 'ASC'),
             ], limit=1)
         if invoice_lines:
             return invoice_lines[0].invoice
@@ -450,8 +473,7 @@ class Fee(ModelSQL,ModelView):
                         invoices,
                         key=lambda invoice: (
                             invoice.invoice_date or datetime.date.min,
-                            invoice.id or 0),
-                        reverse=True)[0]
+                            invoice.id or 0))[0]
 
     def get_landed_status(self,name):
         if self.product:
diff --git a/modules/purchase_trade/view/fee_form.xml b/modules/purchase_trade/view/fee_form.xml
index 2dda642..e46d558 100755
--- a/modules/purchase_trade/view/fee_form.xml
+++ b/modules/purchase_trade/view/fee_form.xml
@@ -17,6 +17,8 @@
     <field name="linked_unit"/>
     <label name="linked_price"/>
     <field name="linked_price"/>
+    <label name="dn_cn"/>
+    <field name="dn_cn"/>
     <!-- <label name="supplier"/>
     <field name="supplier"/>
     <label name="p_r"/>
diff --git a/modules/purchase_trade/view/fee_tree_sequence.xml b/modules/purchase_trade/view/fee_tree_sequence.xml
index 532b730..f0c4e57 100755
--- a/modules/purchase_trade/view/fee_tree_sequence.xml
+++ b/modules/purchase_trade/view/fee_tree_sequence.xml
@@ -19,6 +19,7 @@ this repository contains the full copyright notices and license terms. -->
     <field name="inherit_shipment"/>
     <!-- <field name="purchase"/> -->
     <field name="inv"/>
+    <field name="dn_cn"/>
     <field name="state"/>
     <button string="" name="invoice" width="120"/>
 </tree>
diff --git a/modules/purchase_trade/view/fee_tree_sequence2.xml b/modules/purchase_trade/view/fee_tree_sequence2.xml
index a42989f..20e9190 100755
--- a/modules/purchase_trade/view/fee_tree_sequence2.xml
+++ b/modules/purchase_trade/view/fee_tree_sequence2.xml
@@ -18,6 +18,7 @@ this repository contains the full copyright notices and license terms. -->
     <field name="qt_state"/>
     <!-- <field name="purchase"/> -->
     <field name="inv"/>
+    <field name="dn_cn"/>
     <field name="state"/>
     <button string="" name="invoice" width="120"/>
 </tree>