diff --git a/account_compute_tax_amount/__init__.py b/account_compute_tax_amount/__init__.py
new file mode 100644
index 000000000..b0afae26c
--- /dev/null
+++ b/account_compute_tax_amount/__init__.py
@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+##############################################################################
+#
+#    Author Vincent Renaville. Copyright 2013 Camptocamp SA
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU Affero General Public License as
+#    published by the Free Software Foundation, either version 3 of the
+#    License, or (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU Affero General Public License for more details.
+#
+#    You should have received a copy of the GNU Affero General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+##############################################################################
+
+from . import account_move_line
+# vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:
+
diff --git a/account_compute_tax_amount/__openerp__.py b/account_compute_tax_amount/__openerp__.py
new file mode 100644
index 000000000..a1344d71d
--- /dev/null
+++ b/account_compute_tax_amount/__openerp__.py
@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+##############################################################################
+#
+#    Author Vincent Renaville. Copyright 2013 Camptocamp SA
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU Affero General Public License as
+#    published by the Free Software Foundation, either version 3 of the
+#    License, or (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU Affero General Public License for more details.
+#
+#    You should have received a copy of the GNU Affero General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+##############################################################################
+{
+    "name" : "Recompute tax_amount",
+    "version" : "1.0",
+    "depends" : ["base",
+                 "account",
+                 ],
+    "author" : "Camptocamp",
+    "description": """Recompute tax_amount to avoid sign problem""",
+    'website': 'http://www.camptocamp.com',
+    'data' : [],
+    'installable': True,
+    'active': False,
+}
+# vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:
diff --git a/account_compute_tax_amount/account_move_line.py b/account_compute_tax_amount/account_move_line.py
new file mode 100644
index 000000000..e2e84bbf9
--- /dev/null
+++ b/account_compute_tax_amount/account_move_line.py
@@ -0,0 +1,76 @@
+# -*- coding: utf-8 -*-
+##############################################################################
+#
+# Copyright (c) 2013 Camptocamp (http://www.camptocamp.com)
+# All Right Reserved
+#
+# Author : Vincent Renaville (Camptocamp)
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU Affero General Public License as
+#    published by the Free Software Foundation, either version 3 of the
+#    License, or (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU Affero General Public License for more details.
+#
+#    You should have received a copy of the GNU Affero General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+##############################################################################
+
+from openerp.osv import orm, fields
+import openerp.addons.decimal_precision as dp
+
+
+class account_move_line(orm.Model):
+    _inherit = "account.move.line"
+
+    # We set the tax_amount invisible, because we recompute it in every case.
+    _columns = {
+        'tax_amount': fields.float('Tax/Base Amount',
+                                   digits_compute=dp.get_precision('Account'),
+                                   invisible=True,
+                                   select=True,
+                                   help="If the Tax account is a tax code account, "
+                                        "this field will contain the taxed amount. "
+                                        "If the tax account is base tax code, "
+                                        "this field will contain the basic amount (without tax)."),
+    }
+
+    def create(self, cr, uid, vals, context=None, check=True):
+        result = super(account_move_line, self).create(cr, uid, vals,
+                                                       context=context,
+                                                       check=check)
+        if result:
+            move_line = self.read(cr, uid, result,
+                                  ['credit', 'debit', 'tax_code_id'],
+                                  context=context)
+            if move_line['tax_code_id']:
+                tax_amount = move_line['credit'] - move_line['debit']
+                self.write(cr, uid, [result],
+                           {'tax_amount': tax_amount},
+                           context=context)
+        return result
+
+    def write(self, cr, uid, ids, vals, context=None, check=True, update_check=True):
+        result = super(account_move_line,self).write(cr, uid, ids, vals,
+                                                     context=context,
+                                                     check=check,
+                                                     update_check=update_check)
+        if result:
+            if ('debit' in vals) or ('credit' in vals):
+                move_lines = self.read(cr, uid, ids,
+                                       ['credit', 'debit', 'tax_code_id'],
+                                       context=context)
+                for move_line in move_lines:
+                    if move_line['tax_code_id']:
+                        tax_amount = move_line['credit'] - move_line['debit']
+                        self.write(cr, uid,
+                                   [move_line['id']],
+                                   {'tax_amount': tax_amount},
+                                   context=context)
+
+        return result