Zoho Books > Extensions > SAR Invoicing Regime

Using the SAR Invoicing Regime Extension

This guide explains how to issue invoices and credit notes in Zoho Books after the administrator has configured taxes, SAR Data, RTN, and fiscal templates.

Version 2.0 · Last updated: September 29, 2026

Overview

The extension helps display the Honduras fiscal data required on invoices and credit notes generated from Zoho Books.

Before using: The administrator must have configured taxes, SAR Data records, the RTN field, and the default PDF templates. Users should not create or modify SAR Data unless they have administrative authorization.

Before creating documents

The extension is installed in the correct organization.
The customer has an RTN recorded.
Products or services have the correct taxes.
The invoice or credit note will be created using the default SAR template.

1. Verify the customer's RTN

Before creating an invoice or credit note, confirm that the customer has an RTN recorded. This value appears on the PDF next to the customer information.

Open Sales > Customers.
Select or create the customer.
Look for the custom RTN field.
Enter the customer's RTN without unnecessary additional text.
Save the changes before creating the document.

Expected result: On the PDF, the RTN should appear below the customer name, for example: RTN: 05011970071129.

Customer RTN field used by the extension.

2. Create an invoice

Go to Sales > Invoices.
Click + New.
Select the customer and confirm that the RTN is present.
Enter the invoice date, payment terms, products or services, quantities, prices, and taxes.
Save the invoice, preferably as a draft, to validate the data before sending it.

Wait for the automation: After saving the invoice, wait 30 seconds to 1 minute for the backend automation to run and generate the required data. Then refresh the browser screen to see the data on the document.

3. Create a credit note

Go to Sales > Credit Notes.
Click + New.
Select the customer and add the corresponding products or services.
Save the credit note as a draft or open document, depending on the company's workflow.

Wait for the automation: After saving the credit note, wait 30 seconds to 1 minute. Then refresh the browser to confirm that the fiscal data appears on the document.

4. Validate the generated PDF

Before sending the document to the customer, download or preview the PDF and confirm that it includes the required fiscal fields.

Customer RTN: appears below the customer name.
Fiscal body fields: amount in words, discounts and rebates, exonerated amount, exempt amount, taxable amounts, ISV, and total payable.
SAR footer fields: CAI, issue deadline, and authorized range.
Fiscal legend: “La factura es beneficio de todos. ¡Exíjala!”

Generated SAR invoice — Generated invoice example: highlights the customer RTN, fiscal body fields, and SAR footer data.

Troubleshooting

Issue	Probable cause	What to do
CAI, issue deadline, or authorized range does not appear.	Administrative SAR Data setup is missing or the automation has not finished.	Wait 30 seconds to 1 minute, refresh the browser, and contact the administrator if the issue continues.
The customer's RTN does not appear.	The RTN is empty on the customer record.	Open the customer, complete the RTN, and save again.
Fiscal amounts do not match.	Incorrect taxes or an item without a tax assigned.	Review the taxes on each line and consult the administrator or accountant.
The PDF does not use the fiscal format.	The SAR template is not set as default.	Ask the administrator to review the PDF templates.

Best practices

Review the PDF before sending the first invoice or credit note to a real customer.
Do not send the document immediately after saving it; wait for the automation and refresh.
Validate with your accountant if you have special exoneration, exemption, or withholding rules.
Report any CAI, authorized range, issue deadline, or template issue to the administrator.