Index: tax.py
===================================================================

--- ./modules/account/tax.py
+++ ./modules/account/tax.py
@@ -802,49 +802,52 @@
 
         if self.template:
             vals = self.template._get_tax_value(tax=self)
-            if (self.template.invoice_account
-                    and self.invoice_account.id != template2account.get(
-                        self.template.invoice_account.id)):
+            if (self.template.invoice_account and (not self.invoice_account
+                        or self.invoice_account.id != template2account.get(
+                            self.template.invoice_account.id))):
                 vals['invoice_account'] = template2account.get(
                     self.template.invoice_account.id)
             elif (not self.template.invoice_account
                     and self.invoice_account):
                 vals['invoice_account'] = None
-            if (self.template.credit_note_account
-                    and self.credit_note_account.id != template2account.get(
-                        self.template.credit_note_account.id)):
+            if (self.template.credit_note_account and (not
+                        self.credit_note_account or
+                        self.credit_note_account.id != template2account.get(
+                        self.template.credit_note_account.id))):
                 vals['credit_note_account'] = template2account.get(
                     self.template.credit_note_account.id)
             elif (not self.template.credit_note_account
                     and self.credit_note_account):
                 vals['credit_note_account'] = None
-            if (self.template.invoice_base_code
-                    and self.invoice_base_code.id != template2tax_code.get(
-                        self.template.invoice_base_code.id)):
+            if (self.template.invoice_base_code and (not self.invoice_base_code
+                        or self.invoice_base_code.id != template2tax_code.get(
+                            self.template.invoice_base_code.id))):
                 vals['invoice_base_code'] = template2tax_code.get(
                     self.template.invoice_base_code.id)
             elif (not self.template.invoice_base_code
                     and self.invoice_base_code):
                 vals['invoice_base_code'] = None
-            if (self.template.invoice_tax_code
-                    and self.invoice_tax_code.id != template2tax_code.get(
-                        self.template.invoice_tax_code.id)):
+            if (self.template.invoice_tax_code and (not self.invoice_tax_code
+                        or self.invoice_tax_code.id != template2tax_code.get(
+                        self.template.invoice_tax_code.id))):
                 vals['invoice_tax_code'] = template2tax_code.get(
                     self.template.invoice_tax_code.id)
             elif (not self.template.invoice_tax_code
                     and self.invoice_tax_code):
                 vals['invoice_tax_code'] = None
-            if (self.template.credit_note_base_code
-                    and self.credit_note_base_code.id != template2tax_code.get(
-                        self.template.credit_note_base_code.id)):
+            if (self.template.credit_note_base_code and (not
+                        self.credit_note_base_code or
+                        self.credit_note_base_code.id != template2tax_code.get(
+                        self.template.credit_note_base_code.id))):
                 vals['credit_note_base_code'] = template2tax_code.get(
                     self.template.credit_note_base_code.id)
             elif (not self.template.credit_note_base_code
                     and self.credit_note_base_code):
                 vals['credit_note_base_code'] = None
-            if (self.template.credit_note_tax_code
-                    and self.credit_note_tax_code.id != template2tax_code.get(
-                        self.template.credit_note_tax_code.id)):
+            if (self.template.credit_note_tax_code and (not
+                        self.credit_note_tax_code or
+                        self.credit_note_tax_code.id != template2tax_code.get(
+                        self.template.credit_note_tax_code.id))):
                 vals['credit_note_tax_code'] = template2tax_code.get(
                     self.template.credit_note_tax_code.id)
             elif (not self.template.credit_note_tax_code
@@ -1118,8 +1121,6 @@
         res = {}
         if not rule_line or rule_line.group != self.group:
             res['group'] = self.group.id if self.group else None
-        if not rule_line or rule_line.origin_tax != self.origin_tax:
-            res['origin_tax'] = self.origin_tax.id if self.origin_tax else None
         if not rule_line or rule_line.sequence != self.sequence:
             res['sequence'] = self.sequence
         if not rule_line or rule_line.template != self:
@@ -1271,16 +1272,19 @@
             vals = self.template._get_tax_rule_line_value(rule_line=self)
             if self.rule.id != template2rule[self.template.rule.id]:
                 vals['rule'] = template2rule[self.template.rule.id]
-            if self.origin_tax:
-                if self.template.origin_tax:
-                    if self.origin_tax.id != \
-                            template2tax[self.template.origin_tax.id]:
-                        vals['origin_tax'] = template2tax[
-                            self.template.origin_tax.id]
-            if self.tax:
-                if self.template.tax:
-                    if self.tax.id != template2tax[self.template.tax.id]:
-                        vals['tax'] = template2tax[self.template.tax.id]
+            if self.template.origin_tax:
+                if (not self.origin_tax or self.origin_tax.id !=
+                        template2tax[self.template.origin_tax.id]):
+                    vals['origin_tax'] = template2tax[
+                        self.template.origin_tax.id]
+            elif self.origin_tax:
+                vals['origin_tax'] = None
+            if self.template.tax:
+                if (not self.tax or self.tax.id !=
+                        template2tax[self.template.tax.id]):
+                    vals['tax'] = template2tax[self.template.tax.id]
+            elif self.tax:
+                vals['tax'] = None
             if vals:
                 self.write([self], vals)
             template2rule_line[self.template.id] = self.id