[IMP] Taxes data should not be editable if linked move is not in draft

account_move_line_tax_editable/__init__.py

@@ -0,0 +1 @@
+from . import models

account_move_line_tax_editable/__manifest__.py

@@ -5,7 +5,7 @@
 {
     'name': 'Account Move Line Tax Editable',
     'summary': """
-        Allows to edit taxes on account move lines""",
+        Allows to edit taxes on non-posted account move lines""",
     'version': '10.0.1.0.0',
     'license': 'AGPL-3',
     'author': 'ACSONE SA/NV,Odoo Community Association (OCA)',

account_move_line_tax_editable/models/__init__.py

@@ -0,0 +1 @@
+from . import account_move_line

account_move_line_tax_editable/models/account_move_line.py

@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 ACSONE SA/NV
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from odoo import api, fields, models
+
+
+class AccountMoveLine(models.Model):
+
+    _inherit = 'account.move.line'
+
+    is_tax_editable = fields.Boolean(
+        string="Is tax data editable?", compute='_compute_is_tax_editable')
+
+    @api.multi
+    @api.depends('move_id.state')
+    def _compute_is_tax_editable(self):
+        for rec in self:
+            rec.is_tax_editable = rec._get_is_tax_editable()
+
+    @api.multi
+    def _get_is_tax_editable(self):
+        self.ensure_one()
+        return self.move_id.state == 'draft'

account_move_line_tax_editable/views/account_move.xml

@@ -11,8 +11,10 @@
         <field name="inherit_id" ref="account.view_move_form"/>
         <field name="arch" type="xml">
             <xpath expr="//field[@name='line_ids']/tree/field[@name='name']" position="after">
-                <field name="tax_line_id"/>
-                <field name="tax_ids" widget="many2many_tags"/>
+                <field name="is_tax_editable" invisible="1"/>
+                <field name="tax_line_id" attrs="{'readonly': [('is_tax_editable', '=', False)]}"/>
+                <field name="tax_ids" attrs="{'readonly': [('is_tax_editable', '=', False)]}"
+                       widget="many2many_tags"/>
             </xpath>
         </field>
     </record>

account_move_line_tax_editable/views/account_move_line.xml

@@ -10,11 +10,16 @@
         <field name="model">account.move.line</field>
         <field name="inherit_id" ref="account.view_move_line_form"/>
         <field name="arch" type="xml">
+            <field name="tax_line_id" position="before">
+                <field name="is_tax_editable" invisible="1"/>
+            </field>
             <field name="tax_line_id" position="attributes">
                 <attribute name="readonly">0</attribute>
+                <attribute name="attrs">{'readonly': [('is_tax_editable', '=', False)]}</attribute>
             </field>
             <field name="tax_ids" position="attributes">
                 <attribute name="readonly">0</attribute>
+                <attribute name="attrs">{'readonly': [('is_tax_editable', '=', False)]}</attribute>
             </field>
         </field>
     </record>