=== modified file 'sale/sale.py'
--- old/sale/sale.py	2009-07-02 14:56:52 +0000
+++ new/sale/sale.py	2009-08-01 17:38:28 +0000
@@ -378,6 +378,8 @@
             'payment_term': pay_term,
             'fiscal_position': order.partner_id.property_account_position.id
         }
+        if context.get('date_inv', False):
+            inv['date_invoice'] = context['date_inv']
         inv_obj = self.pool.get('account.invoice')
         inv.update(self._inv_get(cr, uid, order))
         inv_id = inv_obj.create(cr, uid, inv)
@@ -389,10 +391,16 @@
         return inv_id
 
 
-    def action_invoice_create(self, cr, uid, ids, grouped=False, states=['confirmed','done','exception']):
+    def action_invoice_create(self, cr, uid, ids, grouped=False, states=['confirmed','done','exception'], date_inv=False):
         res = False
         invoices = {}
         invoice_ids = []
+        context = {}
+
+        # If date was specified, use it as date invoiced, usefull when invoices are generated this month and put the 
+        # last day of the last month as invoice date
+        if date_inv:
+            context['date_inv'] = date_inv
 
         for o in self.browse(cr,uid,ids):
             lines = []
@@ -411,7 +419,7 @@
         picking_obj=self.pool.get('stock.picking')
         for val in invoices.values():
             if grouped:
-                res = self._make_invoice(cr, uid, val[0][0], reduce(lambda x,y: x + y, [l for o,l in val], []))
+                res = self._make_invoice(cr, uid, val[0][0], reduce(lambda x,y: x + y, [l for o,l in val], []), context=context)
                 for o,l in val:
                     self.write(cr, uid, [o.id], {'state' : 'progress'})
                     if o.order_policy=='picking':
@@ -419,7 +427,7 @@
                     cr.execute('insert into sale_order_invoice_rel (order_id,invoice_id) values (%s,%s)', (o.id, res))
             else:
                 for order, il in val:
-                    res = self._make_invoice(cr, uid, order, il)
+                    res = self._make_invoice(cr, uid, order, il, context=context)
                     invoice_ids.append(res)
                     self.write(cr, uid, [order.id], {'state' : 'progress'})
                     if order.order_policy=='picking':

=== modified file 'sale/wizard/make_invoice.py'
--- old/sale/wizard/make_invoice.py	2009-01-22 11:23:33 +0000
+++ new/sale/wizard/make_invoice.py	2009-08-01 14:42:14 +0000
@@ -28,11 +28,14 @@
 <form string="Create invoices">
     <separator colspan="4" string="Do you really want to create the invoices ?" />
     <field name="grouped" />
+    <newline />
+    <field name="invoice_date" />
 </form>
 """
 
 invoice_fields = {
-    'grouped' : {'string':'Group the invoices', 'type':'boolean', 'default': lambda x,y,z: False}
+    'grouped' : {'string':'Group the invoices', 'type':'boolean', 'default': lambda x,y,z: False},
+    'invoice_date': {'string': 'Invoiced date', 'type':'date', 'help': 'Usefull if the invoice was created the next month'},
 }
 
 ack_form = """<?xml version="1.0"?>
@@ -46,7 +49,7 @@
     order_obj = pooler.get_pool(cr.dbname).get('sale.order')
     newinv = []
 
-    order_obj.action_invoice_create(cr, uid, data['ids'], data['form']['grouped'])
+    order_obj.action_invoice_create(cr, uid, data['ids'], data['form']['grouped'], date_inv=data['form']['invoice_date'])
     for id in data['ids']:
         wf_service = netsvc.LocalService("workflow")
         wf_service.trg_validate(uid, 'sale.order', id, 'manual_invoice', cr)