Hi, we have to inherit the corresponding report template to change the title.

You can use the following code to change the title of the invoice report from 'Invoice' to 'FACTURA'.

<template id="custom_report_invoice_document"
        inherit_id="account.report_invoice_document">
    <xpath expr="t[@t-call='web.external_layout']" position="replace">
        <t t-call="web.html_container">
            <div class="mt-5 clearfix">
                <div class="page mb-4">
                    <h2>
                        <h1 t-if="o.move_type == 'out_invoice' and o.state == 'posted'"
                            style="font-size: 40px;  text-align: center; margin-bottom:2px; font-weight: bold;">
                            FACTURA
                        </h1>
                    </h2>
                </div>
            </div>
        </t>
    </xpath>
</template>

Hope it helps

Steps:

1. Activate Developer Mode:
   • Go to Settings > Activate Developer Mode.
2. Go to Translations:
   • Navigate to Settings > Translations > Application Terms.
3. Find the "INVOICE" Term:
   • Search for the term "Invoice" in the list. This will show the default translation for invoices.
4. Edit the Translation:
   • Find the term "Invoice" in the language you're working with (for example, if you're working with Spanish, it would be in the "Spanish (Spain)" translation).
   • Modify the translation for "Invoice" to "Factura".
5. Save the Changes:
   • Save the translation, and the change should reflect on all invoices printed in the selected language.

2. Check Language Settings:

If you are using multiple languages, make sure that the invoice report is being printed in the correct language. You can set the language for each user under Settings > Users & Companies > Users. Under each user, you can set their preferred language (e.g., Spanish).

Thanks & Regards,

Email :-  contact@datainteger.com