odoo_source/addons/account/data/mail_template_data.xml

<?xml version="1.0" ?>
<odoo>

    <!-- Mail template are declared in a NOUPDATE block
         so users can freely customize/delete them -->
    <data noupdate="1">
        <!--Email template -->
        <record id="email_template_edi_invoice" model="mail.template">
            <field name="name">Invoicing: Invoice email</field>
            <field name="email_from">${(object.user_id.email and '&quot;%s&quot; &lt;%s&gt;' % (object.user_id.name, object.user_id.email) or '')|safe}</field>
            <field name="subject">${object.company_id.name} Invoice (Ref ${object.number or 'n/a'})</field>
            <field name="partner_to">${object.partner_id.id}</field>
            <field name="model_id" ref="account.model_account_invoice"/>
            <field name="auto_delete" eval="True"/>
            <field name="report_template" ref="account_invoices"/>
            <field name="report_name">Invoice_${(object.number or '').replace('/','_')}_${object.state == 'draft' and 'draft' or ''}</field>
            <field name="lang">${object.partner_id.lang}</field>
            <field name="body_html" type="html">
<div>
<p>Dear ${object.partner_id.name}
% set access_action = object.with_context(force_website=True).get_access_action()
% set is_online = access_action and access_action['type'] == 'ir.actions.act_url'
% set access_url = object.get_mail_url()

% if object.partner_id.parent_id:
    (<i>${object.partner_id.parent_id.name}</i>)
% endif
,</p>
<p>Here is, in attachment, your 
% if object.number:
invoice <strong>${object.number}</strong>
% else:
invoice
% endif
% if object.origin:
(with reference: ${object.origin})
% endif
amounting in <strong>${format_amount(object.amount_total, object.currency_id)}</strong>
from ${object.company_id.name}.
</p>

% if is_online:
    <br/><br/>
    <center>
      <a href="${access_url}" style="background-color: #1abc9c; padding: 20px; text-decoration: none; color: #fff; border-radius: 5px; font-size: 16px;" class="o_default_snippet_text">View Invoice</a>
    </center>
% endif
    <br/><br/>

% if object.state=='paid':
    <p>This invoice is already paid.</p>
% else:
    <p>Please remit payment at your earliest convenience.</p>
% endif

<p>Thank you,</p>
<p style="color:#888888">
% if object.user_id and object.user_id.signature:
    ${object.user_id.signature | safe}
% endif
</p>
</div></field>
        </record>

        <!--Default Notification Email template for invoices-->
        <record id="account.mail_template_data_notification_email_account_invoice" model="mail.template">
            <field name="name">Account: Invoice notification header</field>
            <field name="subject">${object.subject}</field>
            <field name="model_id" ref="mail.model_mail_message"/>
            <field name="auto_delete" eval="True"/>
            <field name="body_html" type="html">
<div>
% set record = ctx.get('record')
% set company = record and record.company_id or ctx.get('company')
<table border="0" width="100%" cellpadding="0" bgcolor="#ededed" style="padding: 20px; background-color: #ededed; border-collapse:separate;" summary="o_mail_notification">
<tbody>
    <!-- HEADER -->
    <tr>
        <td align="center" style="min-width: 590px;">
            <table width="590" border="0" cellpadding="0" bgcolor="#875A7B" style="min-width: 590px; background-color: rgb(135,90,123); padding: 20px; border-collapse:separate;">
                <tr>
                    <td valign="middle">
                        <span style="font-size:20px; color:white; font-weight: bold;">
                            Invoice ${object.record_name}
                        </span>
                    </td>
                    <td valign="middle" align="right">
                        <img src="/logo.png?company=${company.id}" style="padding: 0px; margin: 0px; height: auto; width: 80px;" alt="${company.name}"/>
                    </td>
                </tr>
          </table>
    </td>
  </tr>
  <!-- CONTENT -->
  <tr>
        <td align="center" style="min-width: 590px;">
            <table width="590" border="0" cellpadding="0" bgcolor="#ffffff" style="min-width: 590px; background-color: rgb(255, 255, 255); padding: 20px; border-collapse:separate;">
                <tbody>
                    <td valign="top" style="font-family:Arial,Helvetica,sans-serif; color: #555; font-size: 14px;">
                        ${object.body | safe}
                    </td>
                </tbody>
            </table>
        </td>
    </tr>
    <!-- FOOTER -->
    <tr>
        <td align="center" style="min-width: 590px;">
            <table width="590" border="0" cellpadding="0" bgcolor="#875A7B" style="min-width: 590px; background-color: rgb(135,90,123); padding: 20px; border-collapse:separate;">
                <tr>
                    <td valign="middle" align="left" style="color: #fff; padding-top: 10px; padding-bottom: 10px; font-size: 12px;">
                        ${company.name}<br/>
                        ${company.phone or ''}
                    </td>
                    <td valign="middle" align="right" style="color: #fff; padding-top: 10px; padding-bottom: 10px; font-size: 12px;">
                        % if company.email:
                        <a href="mailto:${company.email}" style="text-decoration:none; color: white;">${company.email}</a><br/>
                        % endif
                        % if company.website:
                        <a href="${company.website}" style="text-decoration:none; color: white;">
                        ${company.website}
                        </a>
                        % endif
                    </td>
                </tr>
            </table>
        </td>
    </tr>
    <tr>
        <td align="center">
            Powered by <a target="_blank" href="https://www.odoo.com">Odoo</a>.
        </td>
    </tr>
</tbody>
</table>
</div></field>
        </record>

    </data>
</odoo>