Hi Mohamed,

Yes you can and it is quite easy. When you look at a QWeb report in Odoo you will always see a call at the very top of the report to another template. For example for the sale report:

<template id="report_saleorder_document">
    <t t-call="report.external_layout">
        <!-- Lots of irrelevant code -->
    </t>
</template>

This <t t-call="report.external_layout"> refers to the default report header in Odoo. When you look at that code you'll see this calls another two templates:

<template id="external_layout">
    <!-- Multicompany -->
    <t t-if="not o and doc">
        <t t-set="o" t-value="doc"/>
    </t>
    <t t-if="o and 'company_id' in o">
        <t t-set="company" t-value="o.company_id"></t>
    </t>
    <t t-if="not o or not 'company_id' in o">
        <t t-set="company" t-value="res_company"></t>
    </t>
    <t t-call="report.external_layout_header" />
    <t t-raw="0" />
    <t t-call="report.external_layout_footer" />
</template>

So if you create another template like the one above, which does a call to another (custom made) header & footer you can use them in your custom / other reports.
Something along the lines of:

<template id="external_layout_custom">
    <!-- Multicompany -->
    <t t-if="not o and doc">
        <t t-set="o" t-value="doc"/>
    </t>
    <t t-if="o and 'company_id' in o">
        <t t-set="company" t-value="o.company_id"></t>
    </t>
    <t t-if="not o or not 'company_id' in o">
        <t t-set="company" t-value="res_company"></t>
    </t>
    <t t-call="report.external_layout_header_custom" />
    <t t-raw="0" />
    <t t-call="report.external_layout_footer_custom" />
</template>

Don't forget to also create XML templates for external_layout_header_custom and external_layout_footer_custom too.

Yenthe