How to Start a New GST Invoice Series and File LUT for FY 2026-27?

As India steps into the new Financial Year 2026-27, businesses, accountants, and exporters must immediately update their accounting systems. April marks a critical transition period for Indian taxpayers. It is not just about turning a page on the calendar; it requires active system recalibration to stay aligned with the Goods and Services Tax Network (GSTN) architecture.

Setting up a fresh, unique invoice series and filing your Letter of Undertaking (LUT) are two mandatory tasks that cannot wait. Skipping or delaying these steps triggers immediate compliance bottlenecks, causes technical errors on the GST portal, and can halt your zero-rated export benefits overnight.

This comprehensive guide breaks down exactly how to transition your invoicing and tax compliance seamlessly into FY 2026-27 without disruption.

Why is a New GST Invoice Numbering Series Mandatory for FY 2026-27?

The core reason to start a fresh invoice series comes down to how the GST portal's central validation database functions. The GSTN system resets its checking parameters at the start of every financial year to ensure uniqueness. However, it retains the history of previous years.

If you attempt to upload an invoice number in April 2026 that matches an invoice number you issued in May 2025, the portal will flag it. It reads the number as a duplicate entry and rejects the transaction entirely. This breaks your GSTR-1 filing sequence and prevents your B2B clients from claiming their rightful Input Tax Credit (ITC).

To prevent systemic errors, lock in clean accounting data, and ensure smooth portal synchronization, strictly adhering to GST invoice numbering rules FY 26-27 is an absolute necessity from day one of the financial year.

What are the Official GST Rules for Formatting Invoice Numbers?

Rule 46 of the CGST Rules, 2017 outlines strict parameters for generating tax invoices. To ensure your invoices are legally compliant and accepted by the GSTN system, your numbering system must follow these explicit rules:

• Character Limit: An invoice number must not exceed 16 characters in total. This includes all letters, numbers, and allowed symbols.
• Structure: It must be consecutive and contain only alphanumeric characters (letters A-Z, numbers 0-9).
• Allowed Special Characters: You are permitted to use only two special characters to separate your segments: the slash (/) and the hyphen (-). Spaces, underscores, or other symbols are strictly prohibited.
• Uniqueness: The sequence must be unique for the specific financial year.

Pro-Tip Examples for FY 2026-27:

• Example 1 (Standard Corporate Format): FGC/26-27/001 (Uses 14 characters, clearly identifies the brand, the financial year, and a 3-digit sequential number).
• Example 2 (Multi-Branch Format): DEL-FGC-2627-012 (Uses 15 characters, identifies a Delhi branch location, the brand, the financial year without slashes, and a sequential number).

What is an LUT in GST, and Why Do Exporters Need It?

Under GST law, export operations are categorized as a Zero-Rated Supply (under Section 16 of the IGST Act). This means that while the goods or services leaving India are technically taxable, the government applies a 0% tax rate to keep Indian exports competitive in the global market.

Exporters have two ways to process this: pay Integrated GST (IGST) upfront during shipping and claim a refund later, or utilize a Letter of Undertaking (LUT).

An LUT is an online declaration where an exporter promises to fulfill all export obligations within the timelines specified by law. By filing an LUT, you gain the legal authority to export goods or services without paying integrated tax (IGST) upfront. This provides an immediate cash flow advantage, ensuring your working capital isn't locked up in government refund pipelines for months.

How to File LUT for FY 2026-27 on the GST Portal Online?

Filing your LUT is a completely online, paperless process that takes less than ten minutes if you follow the right steps. Here is the exact, step-by-step navigation path to complete your registration for the new year:

• Step 1: Open your browser, head to the official GST Portal, and log in securely with your corporate credentials.
• Step 2: Go to the main top menu and navigate through: Services > User Services > Furnish Letter of Undertaking (LUT).
• Step 3: Select the correct financial year from the drop-down menu. Ensure you select 2026-2027.
• Step 4: If you have an approved LUT from the previous year, upload a PDF copy of it under the previous LUT section (if prompted or available).
• Step 5: Read and check the three mandatory declaration checkboxes. These confirm you will export goods within three months of invoicing, or realize service payments in foreign currency within one year.
• Step 6: Fill in the names, occupations, and addresses of two independent witnesses in the fields provided.
• Step 7: Enter the place of filing, select the Authorized Signatory from the drop-down list, and click Sign and File with DSC (Digital Signature Certificate) or Sign and File with EVC (OTP sent to registered mobile/email).

Once submitted, the system instantly generates Form GST RFD-11, and your confirmation notice is available for download. Bookmark this workflow so you know exactly how to file LUT for FY 2026-27 before making your first international shipment of the year.

Which Witness Details are Required for Filing the LUT Form RFD-11?

When filling out Form RFD-11 online, the system requires the details of two independent witnesses to validate your declaration. You must prepare the following accurate data points for both individuals:

1. Full Legal Name: Must match their official government identification (like an Aadhaar or PAN card).
2. Occupation: Their professional designation (e.g., Accountant, Business Consultant, Engineer).
3. Complete Residential/Business Address: A detailed physical address including house/office number, street, city, state, and pin code.
4. Note: Witnesses do not need to sign digitally on the portal; their details are simply declared by the authorized signatory during submission.

What Does the Removal of the Export Refund Threshold Mean for Businesses?

In recent compliance updates designed to ease the cost of doing business, the government implemented a critical structural shift: the export refund threshold removed policy.

Previously, micro, small, and medium enterprise (MSME) exporters faced restrictive, rigid minimum thresholds and tedious documentation checks to claim refunds on residual inputs and accumulated credits. This frequently trapped smaller amounts of capital within system loops, as the administrative cost of recovery outweighed the minor refund value.

By eliminating these unnecessary bottlenecks, the GSTN has vastly simplified operational routines. MSME exporters can now claim every rupee of legitimate export incentive and input tax refund regardless of the transaction scale, improving liquidity and leveling the playing field for boutique Indian exporters in global trade.

Can You Use Your FY 2025-26 LUT in the New Financial Year?

There is a common, risky misconception among newer exporters that an LUT remains valid until it is altered or canceled by an officer. This is completely false.

An LUT is strictly tied to a single financial year. The document you filed for the previous period automatically expires at midnight on March 31st.

[FY 2025-26 LUT] ───► Expires March 31 ───► Must File New LUT for FY 2026-27 (Before First Export)

 

To prevent disruptions, you must submit a fresh online application for FY 2026-27 before you generate your very first shipping bill or export invoice of the new year. Exporting without a valid, active LUT forces you into the taxable route, requiring upfront IGST payments and creating unnecessary refund delays.

 

Conclusion: How Can You Keep Your Business 100% GST Compliant This Year?

Transitioning into a new financial year doesn't have to be overwhelming. By proactively setting up a compliant, 16-character GST invoice numbering rules FY 26-27 sequence and filing your fresh LUT before your first export run, you insulate your company from audit flags, duplicate invoice rejections, and locked working capital. Early compliance is always cheaper and less stressful than correcting errors after your books close for the month.

Want to eliminate the guesswork entirely? Head over to freegst.co to access our completely free, updated billing templates, automated GST calculators, and compliance toolkits designed to keep your business running smoothly throughout FY 2026-27.

FAQ: What are the Most Common Questions About FY 2026-27 Invoicing & LUT?

Q1: Is a new invoice series mandatory if I use the e-Invoicing system?

Yes. The e-Invoicing system relies entirely on the primary validation rules of the GST portal. If your underlying ERP or billing software generates a duplicate invoice number from a previous year, the Invoice Registration Portal (IRP) will reject it and refuse to generate an Invoice Reference Number (IRN) or QR code.

Q2: What happens if I export goods without filing the LUT for the current FY?

If you export goods or services without an active, approved LUT for FY 2026-27, the transaction cannot be legally treated as a zero-rated supply without tax. You will be penalized or forced to pay the full applicable IGST amount on the shipment upfront, and then go through the lengthy process of filing a manual refund claim via Form GST RFD-01.

Q3: Is there any official government fee to file an LUT online?

No. The Government of India does not charge any official processing fee, application fee, or portal tax to submit an LUT via Form RFD-11. It is a completely free self-declaration utility provided to boost Indian exports.

Author Note

Kanan Gautam is a GST and business compliance content specialist associated with FreeGST.co. She regularly researches GST registration, GST amendments, GST returns, e-invoicing, MSME compliance, and regulatory updates issued by GSTN, CBIC, GST Council, and the Ministry of Finance. Her content focuses on simplifying complex tax and compliance topics for business owners, startups, professionals, and MSMEs across India.