How to identify the LUT number?

Congratulations on receiving your Letter of Undertaking (LUT) from GST! Form 11A contains two numbers: 1. ARN (Application Reference Number) 2. LUT Number (also known as the GST LUT Reference Number) The LUT Number is the one you should use for your invoice. This number is unique to your LUT application and serves as a reference for your Letter of Undertaking. To confirm, the LUT Number is usually a 17-digit number, starting with "LUT". Please ensure you use this LUT Number on your invoices, as it's a required field for GST compliance.

Thank you for your prompt response Sir. I only see two numbers in the email and on Form 11A too (AD2709XX0XX707W and ZD2XX924XX03X71), which is causing confusion. which one is the LUT number?

The Letter of Undertaking (LUT) does not have a specific LUT number like other GST-related forms. Instead, the important details you need for exporting goods or services without paying IGST (Integrated Goods and Services Tax) are:

1. Application Reference Number (ARN): This is the number assigned to your LUT application. In your case, it is AD2709XX0XX707W, as mentioned in the email. The ARN is useful for tracking the status of your LUT application.

2. Reference Number (Order Number): This is the reference number you received after the LUT application was deemed approved. The email indicates this number as ZD2XX924XX03X71. This reference number is what you will typically mention in your invoices when exporting under LUT.

For Invoices:

When creating your invoices, you should use the Reference Number (Order Number): ZD2XX924XX03X71 on your export invoices as proof that you have an approved LUT for the relevant financial year.

Steps:

• Mention ZD2XX924XX03X71 as your LUT reference in all export invoices.
• Keep the ARN (AD2709XX0XX707W) for your records, as it helps track your application but does not need to be mentioned in invoices.

This ensures your exports are valid under the LUT and exempt from IGST.

Thank you very much for the detailed explanation; I truly appreciate it!

My pleasure sir always to be able to reply to the queries posted in our group...

The LUT reference number is the Application Reference Number (ARN) generated when your LUT (Form GST RFD-11) was approved on the GST portal.

Where to find it:
- Login to GST portal (gst.gov.in)
- Go to Services, then Refunds, then My Saved/Submitted Applications
- Look for Form GST RFD-11 applications
- The ARN is the 15-character reference number starting with ZS

On your export invoices, the standard text to include is:
SUPPLY MEANT FOR EXPORT UNDER LUT WITHOUT PAYMENT OF IGST

Adding the LUT ARN on every invoice is not strictly mandated by GST rules, but many businesses include it as: LUT ARN: ZS[state code][year][sequence] for clarity during audits and reconciliation.

LUT is valid for the full financial year in which it is filed. Renew it before April 1 each year.

For the full LUT filing process, invoice format requirements, and export compliance checklist, this [GST on export of services guide](https://taxgarden.in/blog/gst-on-export-of-services-zero-rated-place-of-supply-india-2026) has the step-by-step walkthrough.