Hii,
Extend the Report Template (QWeb)
Since QWeb can’t run SQL, you use a t-set with env to perform a model search.
Inside the loop that renders invoice lines (usually in a t-foreach="o.invoice_line_ids"), add:
<t t-set="picking" t-value="env['stock.picking'].search([('name', '=', line.origin)], limit=1)"/>
<t t-if="picking">
<span>Delivered on: <t t-esc="picking.date_done.strftime('%d/%m/%Y')"/></span>
</t>
If the line.origin matches a stock.picking.name, the delivery date (date_done) will be printed on the invoice line.
Example Final Snippet:
<tr t-foreach="o.invoice_line_ids" t-as="line">
<td>
<t t-esc="line.name"/>
<t t-set="picking" t-value="env['stock.picking'].search([('name', '=', line.origin)], limit=1)"/>
<t t-if="picking">
<br/>
<small>Delivered on: <t t-esc="picking.date_done.strftime('%d/%m/%Y')"/></small>
</t>
</td>
<!-- other columns like quantity, price, etc. -->
</tr>