diff --git a/addons/account_lock/__init__.py b/addons/account_lock/__init__.py
new file mode 100644
index 00000000000..cde864bae21
--- /dev/null
+++ b/addons/account_lock/__init__.py
@@ -0,0 +1,3 @@
+# -*- coding: utf-8 -*-
+
+from . import models
diff --git a/addons/account_lock/__openerp__.py b/addons/account_lock/__openerp__.py
new file mode 100644
index 00000000000..67e76b49098
--- /dev/null
+++ b/addons/account_lock/__openerp__.py
@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+{
+    'name' : 'Irreversible Lock Date',
+    'version' : '1.0',
+    'category': 'Accounting',
+    'description': """
+    Make the lock date irreversible:
+
+    * You cannot define stricter conditions on advisors than on users. Then, the lock date on advisor must be set before the lock date for users.
+    * You cannot lock a period that is not finished yet. Then, the lock date for advisors must be set before the last day of the previous month.
+    * The new lock date for advisors must be set after the previous lock date.
+    """,
+    'depends' : ['account'],
+    'data': [],
+}
diff --git a/addons/account_lock/i18n/account_lock.pot b/addons/account_lock/i18n/account_lock.pot
new file mode 100644
index 00000000000..8015c500a2f
--- /dev/null
+++ b/addons/account_lock/i18n/account_lock.pot
@@ -0,0 +1,46 @@
+µ# Translation of Odoo Server.
+# This file contains the translation of the following modules:
+#	* account_lock
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: Odoo Server 9.0e\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2018-03-14 08:33+0000\n"
+"PO-Revision-Date: 2018-03-14 08:33+0000\n"
+"Last-Translator: <>\n"
+"Language-Team: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: \n"
+"Plural-Forms: \n"
+
+#. module: account_lock
+#: model:ir.model,name:account_lock.model_res_company
+msgid "Companies"
+msgstr ""
+
+#. module: account_lock
+#: code:addons/account_lock/models/res_company.py:51
+#, python-format
+msgid "The lock date for advisors is irreversible and can't be removed."
+msgstr ""
+
+#. module: account_lock
+#: code:addons/account_lock/models/res_company.py:55
+#, python-format
+msgid "The new lock date for advisors must be set after the previous lock date."
+msgstr ""
+
+#. module: account_lock
+#: code:addons/account_lock/models/res_company.py:77
+#, python-format
+msgid "You cannot define stricter conditions on advisors than on users. Please make sure that the lock date on advisor is set before the lock date for users."
+msgstr ""
+
+#. module: account_lock
+#: code:addons/account_lock/models/res_company.py:66
+#, python-format
+msgid "You cannot lock a period that is not finished yet. Please make sure that the lock date for advisors is not set after the last day of the previous month."
+msgstr ""
+
diff --git a/addons/account_lock/models/__init__.py b/addons/account_lock/models/__init__.py
new file mode 100644
index 00000000000..fbbf76a47b5
--- /dev/null
+++ b/addons/account_lock/models/__init__.py
@@ -0,0 +1,3 @@
+# -*- coding: utf-8 -*-
+
+import res_company
diff --git a/addons/account_lock/models/res_company.py b/addons/account_lock/models/res_company.py
new file mode 100644
index 00000000000..c6834f298ee
--- /dev/null
+++ b/addons/account_lock/models/res_company.py
@@ -0,0 +1,77 @@
+# -*- coding: utf-8 -*-
+
+import time
+import calendar
+
+from datetime import datetime
+from dateutil.relativedelta import relativedelta
+
+from openerp import fields, models, api, _
+from openerp.exceptions import ValidationError
+from openerp.tools.misc import DEFAULT_SERVER_DATE_FORMAT
+
+
+class ResCompany(models.Model):
+    _inherit = 'res.company'
+
+    @api.multi
+    def write(self, vals):
+        # fiscalyear_lock_date can't be set to a prior date
+        if 'fiscalyear_lock_date' in vals or 'period_lock_date' in vals:
+            self._check_lock_dates(vals)
+        return super(ResCompany, self).write(vals)
+
+    @api.multi
+    def _check_lock_dates(self, vals):
+        '''Check the lock dates for the current companies. This can't be done in a api.constrains because we need
+        to perform some comparison between new/old values. This method forces the lock dates to be irreversible.
+
+        * You cannot define stricter conditions on advisors than on users. Then, the lock date on advisor must be set
+        after the lock date for users.
+        * You cannot lock a period that is not finished yet. Then, the lock date for advisors must be set after the
+        last day of the previous month.
+        * The new lock date for advisors must be set after the previous lock date.
+
+        :param vals: The values passed to the write method.
+        '''
+        period_lock_date = vals.get('period_lock_date') and\
+            time.strptime(vals['period_lock_date'], DEFAULT_SERVER_DATE_FORMAT)
+        fiscalyear_lock_date = vals.get('fiscalyear_lock_date') and\
+            time.strptime(vals['fiscalyear_lock_date'], DEFAULT_SERVER_DATE_FORMAT)
+
+        previous_month = datetime.strptime(fields.Date.today(), DEFAULT_SERVER_DATE_FORMAT) + relativedelta(months=-1)
+        days_previous_month = calendar.monthrange(previous_month.year, previous_month.month)
+        previous_month = previous_month.replace(day=days_previous_month[1]).timetuple()
+        for company in self:
+            old_fiscalyear_lock_date = company.fiscalyear_lock_date and\
+                time.strptime(company.fiscalyear_lock_date, DEFAULT_SERVER_DATE_FORMAT)
+
+            # The user attempts to remove the lock date for advisors
+            if old_fiscalyear_lock_date and not fiscalyear_lock_date and 'fiscalyear_lock_date' in vals:
+                raise ValidationError(_('The lock date for advisors is irreversible and can\'t be removed.'))
+
+            # The user attempts to set a lock date for advisors prior to the previous one
+            if old_fiscalyear_lock_date and fiscalyear_lock_date and fiscalyear_lock_date < old_fiscalyear_lock_date:
+                raise ValidationError(_('The new lock date for advisors must be set after the previous lock date.'))
+
+            # In case of no new fiscal year in vals, fallback to the oldest
+            if not fiscalyear_lock_date:
+                if old_fiscalyear_lock_date:
+                    fiscalyear_lock_date = old_fiscalyear_lock_date
+                else:
+                    continue
+
+            # The user attempts to set a lock date for advisors prior to the last day of previous month
+            if fiscalyear_lock_date > previous_month:
+                raise ValidationError(_('You cannot lock a period that is not finished yet. Please make sure that the lock date for advisors is not set after the last day of the previous month.'))
+
+            # In case of no new period lock date in vals, fallback to the one defined in the company
+            if not period_lock_date:
+                if company.period_lock_date:
+                    period_lock_date = time.strptime(company.period_lock_date, DEFAULT_SERVER_DATE_FORMAT)
+                else:
+                    continue
+
+            # The user attempts to set a lock date for advisors prior to the lock date for users
+            if period_lock_date < fiscalyear_lock_date:
+                raise ValidationError(_('You cannot define stricter conditions on advisors than on users. Please make sure that the lock date on advisor is set before the lock date for users.'))
diff --git a/addons/l10n_fr_certification/__openerp__.py b/addons/l10n_fr_certification/__openerp__.py
index 426eabf66ef..9f3ace19d64 100644
--- a/addons/l10n_fr_certification/__openerp__.py
+++ b/addons/l10n_fr_certification/__openerp__.py
@@ -19,7 +19,7 @@ The module adds following features:
 
     Access to download the mandatory Certificate of Conformity delivered by Odoo SA (only for Odoo Enterprise users)
 """,
-    'depends': ['l10n_fr'],
+    'depends': ['l10n_fr', 'account_lock'],
     'installable': True,
     'auto_install': False,
     'application': False,