Hi,

By default we have the barcode in the picking operations report

So you can xpath the same in the template of delivery slip report

for example you can try the code below

<template
    id="report_delivery_document_extends_add_barcode_in_report"
    inherit_id="stock.report_delivery_document">
    <xpath expr="//h2" position="before">
        <div class="row justify-content-end mb16">
            <div class="col-4" name="right_box">
                <img
                    t-att-src="'/report/barcode/?type=%s&amp;value=%s&amp;width=%s&amp;height=%s' % ('Code128', o.name, 600, 100)"
                    style="width:300px;height:50px;" alt="Barcode" />
            </div>
        </div>
    </xpath>
</template>

Regards