India GST E-Invoicing Requirements: Complete IRN & IRP Guide

India's GST e-invoicing system requires businesses above a specified turnover threshold to register every B2B invoice with a government-authorized Invoice Registration Portal (IRP) before issuing it to the buyer. The IRP validates the invoice data against GST rules, generates a unique Invoice Reference Number (IRN) for each document, digitally signs the payload, and returns a JSON file embedded with a QR code. No invoice is legally valid under GST without this IRN. The mandate has expanded in six phases since its launch, from businesses with aggregate turnover exceeding Rs 500 crore in October 2020 down to those exceeding Rs 5 crore from 1 August 2023 (Notification 10/2023-Central Tax). As of October 2026, Rs 5 crore is still the threshold in force: no later notification has lowered it. Any business whose turnover has crossed that line in any financial year since 2017-18 is in scope, and needs to understand the system from end to end.

What makes India's approach architecturally distinct is its centralized clearance model. If you look at how e-invoicing systems work across different countries, you will find considerable variation: some European models route invoices directly between trading parties through PEPPOL access points, others use post-audit reporting, and a few employ real-time clearance. India chose a centralized registration gateway. Every B2B invoice must pass through the IRP, which acts as the single validation authority. The portal checks for duplicates, verifies GSTIN details, confirms schema compliance, and only then assigns the IRN and digital signature. Without that validation step, the invoice carries no legal weight for GST purposes. The IRP is not merely a reporting destination: it is the gatekeeper that determines whether an invoice exists in the eyes of the tax system.

This centralized design creates a chain of downstream consequences that reaches well beyond the invoice itself. The IRN ties directly into GSTR-1 auto-population, meaning validated e-invoices flow automatically into your sales return without manual data entry. Once your GSTR-1 is filed, the same data reaches your buyer's Input Tax Credit (ITC) reconciliation through GSTR-2B, and the e-invoice details link to e-way bill generation for goods in transit. A failure at the registration stage does not just mean a non-compliant invoice. It breaks the entire chain from filing through credit claims to logistics documentation. The sections that follow walk through each link in this chain: the IRP registration workflow and how an IRN is generated, the expanding turnover mandate and its timeline, the JSON schema defined in Form GST INV-01, QR code requirements for B2B and B2C transactions, downstream effects on GSTR-1 filing and ITC, penalties for non-compliance, and the practical steps to prepare your systems.

Four institutions govern how this system operates. The GST Council, chaired by the Union Finance Minister with state-level representation, sets the policy direction and recommends threshold changes. The Central Board of Indirect Taxes and Customs (CBIC) translates those recommendations into binding notifications and circulars. The GST Network (GSTN), a technology company jointly owned by the central and state governments, builds and maintains the IT infrastructure underpinning GST compliance. And the National Informatics Centre (NIC), operating under the Ministry of Electronics and IT, runs the two government IRPs that handle invoice registration, validation, and IRN generation, alongside four private IRPs authorised by GSTN.

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How the Invoice Registration Portal Generates an IRN

Every GST e-invoice in India passes through a defined technical workflow before it becomes a legally valid document. Understanding this sequence is essential for ERP administrators configuring system integrations and for finance teams overseeing the compliance process.

The Invoice Registration Portal (IRP) is the government-authorized platform that validates, registers, and returns signed e-invoices. Here is what happens, step by step, when a business registers an invoice:

Step 1: Generate the invoice JSON. Your billing or ERP system produces the invoice data in the prescribed JSON format defined by Form GST INV-01. This schema covers supplier and buyer details, item-level particulars, tax breakdowns, and document metadata. The data must conform exactly to the field specifications before submission.

Step 2: Submit to an authorized IRP via API. The JSON payload is transmitted to one of the government-authorized IRP portals through a RESTful API call. Six IRPs are authorised: NIC IRP-1 (einvoice1.gst.gov.in) and NIC IRP-2, run by the National Informatics Centre, and four private IRPs, Cygnet IRP-3, Clear IRP-4, EY IRP-5 and IRIS IRP-6. All six connect to the same central registration system, so the Invoice Reference Number (IRN) generated is unique across the entire GST network regardless of which portal processes it.

Step 3: The IRP validates the data. On receiving the payload, the IRP runs a series of validation checks:

• GSTIN validity: confirms both supplier and buyer GSTINs are active and correctly formatted
• Mandatory field completeness: verifies all required fields in the JSON schema are populated
• Duplicate detection: checks whether an invoice with the same combination of supplier GSTIN, financial year, document type, and document number has already been registered
• Document age: for suppliers with aggregate annual turnover of Rs 10 crore or more, rejects invoices, credit notes and debit notes dated more than 30 days before the date of reporting (see the reporting window below)

If any check fails, the IRP returns an error response with specific codes identifying the problem. Your system must handle these errors and either correct the data or flag it for manual review.

Step 4: IRN generation. When validation passes, the IRP generates a unique 64-character Invoice Reference Number (IRN). This hash is computed from four components: the supplier's GSTIN, the financial year, the document type code, and the document number. Because the hash inputs are unique per invoice, the resulting IRN is a deterministic, non-repeating identifier for that specific document.

Step 5: Digital signing. The IRP digitally signs the entire JSON payload using its private key. This signature serves as the government's authentication that the invoice data was registered through an authorized channel and has not been altered after registration.

Step 6: Return the signed payload. The IRP sends back the digitally signed JSON, now containing the IRN and a generated QR code, to the submitting system. Your ERP or billing software must capture and store this response.

Step 7: Include IRN and QR code on the invoice. The supplier is required to print or embed both the IRN and the QR code on the invoice document provided to the buyer, whether in PDF or paper format. An invoice without these elements is not a valid e-invoice under the GST framework.

Beyond returning the signed data to the supplier, the IRP also pushes the registered e-invoice data directly to the GST portal. This automatic transmission is what enables downstream auto-population of GSTR-1 returns, a process covered in detail in a later section of this guide.

Cancellation window. A registered e-invoice can be cancelled through the IRP within 24 hours of generation. Cancellation is refused even inside that window if an e-way bill generated against the invoice is still active or has been verified in transit, and the number of a cancelled invoice cannot be used again for a new IRN. After the 24-hour window closes, cancellation through the portal is no longer possible. The supplier must instead issue a credit note or debit note to adjust or reverse the original invoice, following standard GST procedures for those document types.

India's centralized portal model, where every invoice must pass through a government-operated registration system before it is considered valid, shares architectural similarities with approaches adopted by other countries. Poland's KSeF centralized e-invoicing portal, for instance, also requires businesses to register invoices through a single national platform before they can be issued to buyers. For organizations operating across multiple jurisdictions, recognizing these structural parallels can simplify the process of designing integration architectures that accommodate more than one country's requirements.

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The Expanding Mandate: From Rs 500 Crore to Rs 5 Crore

When CBIC (Central Board of Indirect Taxes and Customs) launched mandatory e-invoicing in October 2020, it applied only to the largest enterprises. Since then, the turnover threshold has been progressively reduced, with each phase pulling a new wave of businesses into scope.

Complete Threshold Timeline

That is five reductions in under three years after launch, and none since August 2023. The Rs 5 crore threshold has now stood for longer than any phase before it.

How the Threshold Applies

The mandate uses Annual Aggregate Turnover (AATO) as its measure. This is the total turnover across all GSTINs registered under a single PAN, calculated for any preceding financial year from 2017-18 onward. It includes taxable supplies, exempt supplies, exports, and inter-state supplies.

One critical rule catches many businesses off guard: the obligation is permanent once triggered. If your aggregate turnover exceeded the applicable threshold in any financial year since 2017-18, you remain subject to e-invoicing even if your revenue drops below that threshold in later years. A company whose turnover exceeded Rs 5 crore in FY 2023-24 but fell to Rs 4 crore in FY 2025-26 still must generate e-invoices for every applicable transaction.

Who Is Currently Exempt

Several categories of registered persons remain outside the e-invoicing mandate regardless of turnover, under Notification 13/2020-Central Tax as amended:

• SEZ units (Special Economic Zone units, though SEZ developers are covered)
• Insurers and banking companies and financial institutions (including NBFCs)
• Goods Transport Agencies (GTAs) supplying services of transporting goods by road
• Passenger transport service providers
• Suppliers of admission to the exhibition of cinematograph films in multiplex screens
• Government departments and local authorities, exempted from 1 June 2021 by Notification 23/2021-Central Tax
• OIDAR suppliers registered under Rule 14 (Online Information and Database Access or Retrieval services supplied from outside India)

Most of these sectors already issue their own prescribed documents under Rule 54 of the CGST Rules in place of a standard tax invoice: consolidated statements for insurers and banks, consignment notes for GTAs, tickets for passenger transport and multiplex admission. The exemption attaches to the registered person, not the transaction, and it can be narrowed by a later notification, so businesses in exempt categories should still watch CBIC notifications.

The Revenue Context

The scale of the mandate mirrors the scale of GST itself. According to the Indian government's eight-year assessment of GST, India's gross GST revenue reached a record Rs 22.08 lakh crore (approximately USD 260 billion) in FY 2024-25, reflecting 9.4 percent year-on-year growth, with the active taxpayer base expanding to over 1.51 crore registrations. The same assessment credits the rise to the economy's growing formalisation and improved tax compliance, and lists B2B e-invoicing, now mandatory above Rs 5 crore, among the GST Council's notable decisions.

For a business nearing Rs 5 crore, the takeaway is that preparation should start before the line is crossed. The test looks at preceding financial years, so the obligation begins on the first day of the year after the one in which turnover exceeds Rs 5 crore, and no separate notice announces it. When the threshold moved, notice was short too: across the five reductions since launch, the gap between notification and start date ran from about three weeks (Notification 5/2021, issued 8 March 2021 for 1 April) to just under three months (Notification 10/2023, issued 10 May 2023 for 1 August).

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Inside Form GST INV-01: The E-Invoice JSON Schema

The e-invoice data structure is defined by Form GST INV-01, a JSON schema in which a core set of fields is mandatory on every invoice, others become mandatory only for certain transaction types, and the rest are optional. This schema is the contract between your billing system and the IRP. Every field must conform to prescribed data types, lengths, and validation rules before the IRP will accept the payload and generate an IRN. The NIC provides an API sandbox at einv-apisandbox.nic.in where developers and ERP administrators can test their JSON payloads against production validation rules before going live.

Understanding the mandatory field groups is essential for ERP configuration and data quality. Rather than listing every field, the following breakdown covers the groups your system must populate correctly.

Transaction details form the document header. These include the supply type (B2B, B2C, export, SEZ), document type (invoice, credit note, debit note), document number, and document date. The document number must follow the GST format: a maximum of 16 alphanumeric characters with permitted special characters, unique within a financial year per GSTIN. If your team needs the field-level view of what must appear on that underlying tax invoice before it ever reaches the IRP, this Rule 46 checklist for India GST invoices is the closest companion reference.

Supplier details identify the seller. Mandatory fields include the supplier GSTIN, legal name as registered with GST, trade name, registered address (building/street, city), state code, and PIN code. These values must match your GST registration exactly. Even minor discrepancies between your master data and your GST registration will trigger validation failures at the IRP.

Buyer details mirror the supplier structure. The buyer GSTIN, legal name, trade name, address, state code, PIN code, and critically the place of supply are all required for B2B transactions. Place of supply determines whether CGST/SGST or IGST applies, so an incorrect value here cascades into tax calculation errors across every line item.

Item details are captured per line item and carry the bulk of the schema's complexity. Each line requires an HSN code, item description, quantity, unit of measurement, unit price, taxable value, applicable GST rate, and the computed CGST, SGST, or IGST amounts along with the total item value. HSN code accuracy deserves particular attention. The schema requires HSN codes at the line-item level, and incorrect codes trigger immediate validation errors at the IRP. Since 1 April 2021 (Notification 78/2020-Central Tax), the digit requirement follows the preceding financial year's aggregate turnover: 6-digit HSN codes above Rs 5 crore, and at least 4 digits on B2B invoices up to Rs 5 crore. Because e-invoicing applies to anyone who exceeded Rs 5 crore in any year since 2017-18, an e-invoicing business whose turnover last year was below Rs 5 crore may correctly be using 4-digit codes. If your product master data contains outdated or imprecise HSN classifications, you will encounter repeated rejections.

Value details aggregate the line-item totals into document-level summaries: total taxable value, total CGST, total SGST, total IGST, total invoice value, and any rounding-off amount. These computed totals must reconcile with the sum of individual line items. The IRP validates this arithmetic, so rounding discrepancies even of a single paisa can cause rejections.

Document period fields (from date and to date) apply to recurring service invoices where the supply spans a defined period. While not required for one-time goods transactions, these become mandatory when your invoice covers a service contract or subscription period.

Beyond the mandatory groups, the schema includes optional sections that become relevant for specific transaction types. Export transactions require port code and shipping bill details. Supplies through e-commerce platforms require the operator's GSTIN. Payment details such as payment mode, account number, and payment terms can be included where applicable.

The most common validation errors encountered at the IRP follow predictable patterns. Duplicate document numbers are rejected outright since the IRP enforces uniqueness per GSTIN per financial year. Invalid GSTINs for either the supplier or buyer fail checksum validation before the payload is even processed. Missing mandatory fields return specific error codes identifying which field group is incomplete. And HSN code mismatches, where the code does not exist in the GST HSN master or does not meet the required digit length for the supplier's turnover slab, account for a significant share of first-time integration failures. Running your payloads through the NIC sandbox before production cutover eliminates most of these issues during the testing phase rather than during live operations.

QR Code Requirements: B2B and B2C Distinctions

India's GST e-invoicing framework creates two entirely separate QR code obligations that apply to different transaction types, carry different technical requirements, and serve different purposes. Conflating the two is a common source of confusion, particularly for businesses that handle both B2B and B2C sales.

The B2B E-Invoice QR Code

When the Invoice Registration Portal generates an IRN for a B2B, B2G, or export invoice, it simultaneously produces a QR code that must be printed on the invoice. This QR code is not created by the supplier. It is generated by the IRP as part of the signed response and returned alongside the IRN and digital signature.

According to GSTN's e-invoice FAQ, the QR code encodes nine items:

• Supplier GSTIN and recipient GSTIN
• Invoice number and invoice date
• Invoice value (taxable value plus gross tax)
• Number of line items
• HSN code of the main item (the line with the highest taxable value)
• Invoice Reference Number (IRN)
• IRN generation date

This QR code serves a verification function. A tax officer conducting a roadside inspection of goods in transit can scan the QR and confirm the invoice details against the IRP's records in real time. Recipients can do the same to verify that an invoice they received was genuinely registered on the portal before claiming input tax credit. The QR effectively turns every printed e-invoice into an instantly auditable document, eliminating the need to log into the GST portal for on-the-spot checks.

Because the IRP generates this QR automatically, suppliers do not need separate QR generation software for B2B e-invoices. Your ERP or billing system receives the QR as part of the IRP response and embeds it into the invoice printout.

The B2C Dynamic QR Code: A Separate Obligation

B2C transactions fall outside the e-invoicing mandate entirely. There is no requirement to register B2C invoices on the IRP, no IRN generation, and no IRP-produced QR code. However, a separate and distinct QR code requirement applies to B2C invoices for large businesses.

Businesses with aggregate annual turnover exceeding Rs 500 crore must include a dynamic QR code on their B2C invoices. This is fundamentally different from the B2B e-invoice QR in both purpose and structure. The B2C dynamic QR is a UPI-compatible payment QR code that enables customers to scan the code and pay directly through any UPI application. Under CBIC Circular 146/02/2021 it carries the supplier's GSTIN, UPI ID and bank account with IFSC, alongside the invoice number and date, the total invoice value and the GST amount broken into CGST, SGST, IGST and cess. Those invoice particulars are there to make the payment, not to prove registration: nothing in the B2C QR is checked against an IRP record.

The distinction matters for ERP configuration. Your system needs to handle two separate QR workflows:

A company with turnover above Rs 500 crore that has flawless B2B e-invoicing compliance can still face penalties for missing the dynamic QR on its B2C invoices, because the two obligations are independent. For businesses below the Rs 500 crore threshold, B2C invoices carry no QR code obligation under current rules.

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From E-Invoice to Tax Return: GSTR-1, ITC, and E-Way Bills

Registering an e-invoice with the IRP is not an isolated compliance event. It is the first link in a chain that auto-populates your tax returns, validates your buyer's input tax credit claims, and can simultaneously generate an e-way bill for goods in transit. This interconnected design is what transforms India's e-invoicing from a reporting obligation into the backbone of the entire B2B tax compliance infrastructure.

GSTR-1 Auto-Population

Once the IRP validates and registers an e-invoice, the invoice data is automatically pushed to the GST portal, where the e-invoice details auto-populate the supplier's GSTR-1, the outward supply return that every registered taxpayer must file monthly or quarterly.

This means you do not need to manually re-enter invoice data into your GSTR-1. The auto-populated entries appear in your return draft, where you can review and amend them if needed before filing. For businesses processing hundreds or thousands of B2B invoices per month, this eliminates a major source of data entry errors and duplicate entries that previously plagued the filing process. Auto-population is a facility, not a guarantee, though: an e-invoice that fails the GST portal's own GSTR-1 validations is not populated and lands in a downloadable error report instead, and the supplier remains responsible for what the filed return contains.

The practical effect is significant. Before e-invoicing, suppliers maintained their own invoice records, manually entered them into GSTR-1, and discrepancies between what the supplier reported and what actually existed were common. Auto-population from the IRP closes that gap by making the registered e-invoice the single authoritative source for outward supply reporting.

ITC Enablement for the Buyer

Once the supplier files GSTR-1 (or the quarterly IFF), the invoices it reports populate two critical documents on the buyer's side: GSTR-2A (the auto-drafted inward supply statement) and GSTR-2B (the auto-generated ITC statement, shaped since October 2024 by the buyer's actions in the Invoice Management System). This is where the chain becomes consequential for both parties in the transaction.

A buyer can only claim Input Tax Credit on invoices that appear in their GSTR-2B, and it also needs a valid tax invoice in its possession. The e-invoice decides the second condition. Under Rule 48(5) of the CGST Rules, an invoice issued without an IRN by a supplier that is required to e-invoice is not treated as an invoice at all. The supplier can still type that invoice into GSTR-1 by hand and make it appear in the buyer's GSTR-2B, but the credit rests on a document the law does not recognise, and the buyer's ITC is exposed in any later scrutiny, regardless of whether the goods or services were genuinely received and paid for. For teams building the downstream control layer, this workflow for GST ITC reconciliation across GSTR-2B, IMS, and Rule 37 shows how that portal-fed data is reviewed before credits are finalized.

This creates a direct financial dependency between supplier compliance and buyer tax recovery. A supplier who neglects e-invoice generation does not just risk penalties for themselves. They put their buyer's legitimate tax credits at risk. For buyers managing large vendor bases, this makes supplier e-invoicing compliance a procurement concern, not merely a tax department issue. That same control mindset applies to checking supplier GSTIN details on vendor invoices before releasing payment or ITC. The same vendor-governance discipline also matters when AP teams need Udyam status and acceptance dates for India's MSME payment-deadline rule under Section 43B(h).

It also matters when the payment itself may trigger withholding, because the invoice data feeding GST controls is often the same data AP teams use to check India TDS sections, thresholds, and GST TDS rules on invoice payments.

The connected data flow between IRP registration, GSTR-1, and GSTR-2B is also what has driven measurable improvements in tax administration. For in-scope suppliers, the system leaves little room for invoices that exist in one party's records but not the other's, because every valid B2B invoice must trace back to an IRP-registered document.

E-Way Bill Integration

The third downstream process triggered by e-invoice registration is e-way bill generation. If your e-invoice JSON payload includes both Part A (invoice and item details) and Part B (vehicle number, transporter ID, and transport mode), the system auto-generates an e-way bill simultaneously with the IRN. You do not need to visit the e-way bill portal separately or re-enter consignment details. Teams that need the transport-side operational detail can use this guide to India's e-way bill thresholds, Part A, Part B, and validity rules.

This integration eliminates redundant data entry for transactions that require both documents, which is the common case for consignments above Rs 50,000 moving between states, and intra-state movements wherever the state's own threshold is crossed. Since 1 January 2025, an e-way bill can no longer be generated against a document more than 180 days old. The e-way bill number is generated alongside the IRN and linked to the same underlying invoice data, ensuring consistency between the tax document and the transport document.

The critical operational risk here is the reverse scenario. If an e-invoice is required for a transaction but has not been generated, any e-way bill created independently for that shipment is considered invalid. Goods in transit without a valid e-way bill can be detained at checkpoints, and the transporter faces penalties under both GST and transport regulations. For businesses with active supply chains, a single missed e-invoice can halt a shipment, delay delivery commitments, and trigger penalties that extend well beyond the original compliance failure.

Penalties for Non-Compliance and Cascading Consequences

Failing to generate a valid e-invoice carries direct financial penalties under GST law, but the real exposure extends far beyond the fine itself. Each non-compliant invoice triggers a chain of downstream consequences that affects not just the supplier but the buyer and the physical movement of goods.

Direct Penalties

Three provisions decide the cost of e-invoicing failures:

• Failure to generate an e-invoice: under section 122 of the CGST Act, Rs 10,000 per invoice or an amount equal to the tax evaded on that invoice, whichever is higher. For a high-value transaction where the GST component exceeds Rs 10,000, the penalty scales with the invoice amount.
• Other contraventions, such as errors in an e-invoice: where no specific penalty applies, section 125 imposes a general penalty of up to Rs 25,000. The 57th GST Council (8 October 2026) has recommended cutting that maximum to Rs 10,000, which needs an amendment to the CGST Act and is not yet in force.
• Invoice treated as "not issued": under Rule 48(5), an invoice issued without a valid IRN by a supplier required to e-invoice is not treated as an invoice under GST law. This is not a technical distinction. The invoice cannot be regularized retroactively. It simply does not exist in the eyes of the GST framework.

To put the per-invoice penalty in perspective: a business issuing 100 invoices per month without valid IRNs faces a minimum penalty exposure of Rs 10 lakh per month, before accounting for the tax-proportional penalty on higher-value invoices.

The Cascading Consequences Chain

What makes e-invoicing non-compliance particularly damaging is the way a single failure propagates through multiple systems and affects multiple parties. Without an IRN, the invoice is not recognized as having been issued under GST. Every downstream process described in the previous section breaks simultaneously: the buyer's ITC on a purchase they already paid tax on rests on a document the law does not recognise, even if the supplier reports it in GSTR-1 by hand and it reaches the buyer's GSTR-2B. The supplier's GSTR-1 is not auto-populated, forcing manual entry and creating reconciliation gaps. And if the transaction requires an e-way bill, the absence of a valid e-invoice renders it invalid too, meaning goods in transit can be physically detained at checkpoints.

The cascading nature means your non-compliance becomes your customer's financial problem. The buyer's tax credit is put at risk through no fault of their own. A single missing IRN can halt a shipment. And the exposure compounds: persistent non-compliance across multiple invoices triggers GST audit attention, and the inability to produce valid IRNs for a volume of transactions creates a documentation gap that is difficult to defend during assessment.

If you discover that your business should have been generating e-invoices but has not been doing so, past invoices cannot be retroactively registered with the IRP. The invoices already issued without IRNs remain legally invalid, and the penalty exposure for those periods is real. The practical course of action is to begin compliant e-invoice generation immediately for all new invoices and consult a GST practitioner about voluntary disclosure and potential penalty relief for the non-compliant period.

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Reporting Deadlines, MFA, and Preparing for Compliance

The e-invoicing framework is not static. GSTN changed how businesses interact with the Invoice Registration Portal several times in 2025, and a further extension to reverse-charge self-invoices is now being built. These are the rules in force as of October 2026, and the change that comes next.

The 30-Day Reporting Window

Since 1 April 2025, taxpayers with an aggregate annual turnover of Rs 10 crore or more must report invoices, credit notes and debit notes to the IRP within 30 days of the document date, and the IRP rejects anything older (GSTN advisory on the revised time limit). GSTN's own example: an invoice dated 1 April must be reported by 30 April. The limit began on 1 November 2023 for taxpayers at Rs 100 crore and above, and was then extended down to Rs 10 crore.

GSTN states no such limit for businesses between Rs 5 crore and Rs 10 crore. That is not a licence to report late: the IRN is part of the invoice, so it must still be obtained before the invoice is issued to the buyer.

The consequence of missing the window is straightforward and severe. The IRP will not generate an IRN for a late submission. Without the IRN, the invoice is not treated as an invoice under GST law, which puts the buyer's Input Tax Credit at risk and exposes the seller to penalties under section 122.

Mandatory Two-Factor Authentication

Two-factor authentication became mandatory for the e-invoice and e-way bill portals in three steps, under the GSTN advisory of 17 December 2024: from 1 January 2025 for taxpayers with turnover above Rs 20 crore, from 1 February 2025 above Rs 5 crore, and from 1 April 2025 for every user regardless of turnover. Whether your business sits at Rs 5 crore or Rs 500 crore, every login to the IRP now requires MFA.

For organizations with multiple users generating or managing e-invoices, this means each individual must have MFA configured on their account, and a new user should have it working before the first invoicing cycle they handle.

Invoice Number Case-Insensitivity

Since 1 June 2025, the IRP treats invoice and document numbers as case-insensitive, converting them to uppercase before processing. "INV-2025-001" and "inv-2025-001" are treated as identical, and the second submission is rejected as a duplicate. The rule applies to documents dated from 1 June 2025; IRNs generated earlier are unaffected.

This change has real implications for businesses whose billing or ERP systems treat invoice numbers as case-sensitive. If your numbering scheme relies on mixed-case distinctions to differentiate invoices, branches, or series, those series now collide. Audit your invoice number formats and confirm that converting everything to uppercase produces no duplicates.

E-Invoicing for Reverse-Charge Self-Invoices

Until now, the self-invoice a recipient raises when it pays tax under the reverse charge mechanism has stayed outside the IRP. That is changing. On 8 October 2026 the 57th GST Council recommended extending e-invoicing to domestic supplies received from unregistered persons where tax is payable under reverse charge, and to the import of services, for taxpayers with aggregate annual turnover of Rs 5 crore and above.

GSTN followed with Advisory No. 678 on 16 October 2026, adding two new supply types to the e-invoice schema: RCMDOM for self-invoices on specified domestic supplies from unregistered persons, and RCMIMP for self-invoices on imported services. Here the recipient, not the supplier, generates the IRN. Both are live in the sandbox of all six IRPs, while the production date and the start of the reporting requirement are still to be announced, along with the notifications that will make it law.

For a business that already self-invoices under India's GST reverse charge and self-invoice rules, the practical step now is to have the ERP team build and test RCMDOM and RCMIMP payloads in the sandbox before the start date is fixed.

Preparing to Come Into Scope

If your business is approaching or has recently crossed the Rs 5 crore aggregate turnover mark, preparation should begin before e-invoicing becomes mandatory for you. The following steps cover the essential groundwork.

Verify your turnover status. Aggregate turnover is calculated across all GSTINs under a single PAN, and the relevant period extends back to any financial year from 2017-18 onward. If your turnover exceeded Rs 5 crore in any of those years, you are already in scope even if current-year revenue is lower.

Assess your billing system's readiness. Your ERP or accounting software must be capable of generating invoice data in the Form GST INV-01 JSON schema and integrating with the IRP's APIs. If your current system cannot produce the required JSON output, you need either an upgrade, a middleware solution, or a different billing platform entirely.

Review HSN code accuracy. Every line item on an e-invoice requires a valid HSN or SAC code. The digit length follows the preceding financial year's turnover: 6-digit codes above Rs 5 crore, at least 4 digits up to Rs 5 crore. Inaccurate or missing HSN codes will cause the IRP to reject the invoice outright.

Test in the sandbox environment. The NIC provides an API sandbox at einv-apisandbox.nic.in where you can submit test payloads and validate your integration before going live. Use it extensively. Discovering schema errors or authentication issues in production means failed invoices and compliance gaps.

Ensure invoice numbering compatibility. Under the case-insensitivity rule in force since June 2025, confirm that your invoice number series will not produce duplicates when converted to uppercase, and fix the numbering logic before go-live rather than troubleshooting rejection errors later.

Set up MFA for all portal users. Two-factor authentication is mandatory for every IRP login, so every person in your organization who will access the e-invoice portal needs it configured and tested before their first real submission.

Preparation also covers the purchase side, since invoices from in-scope suppliers must carry an IRN and QR code. Checking them before claiming credit means reading the IRN, GSTINs, HSN codes and tax amounts off each one, and where those invoices still arrive as PDFs, automated invoice data extraction tools can pull those fields into spreadsheet rows ready to reconcile against GSTR-2B. Keying them in by hand at volume invites the kind of errors that let an invoice without a valid IRN slip through.

India's e-invoicing mandate has moved steadily in one direction since 2020: a threshold cut from Rs 500 crore to Rs 5 crore, a 30-day reporting window, mandatory MFA, and next, reverse-charge self-invoices on the IRP. Whether you are already generating e-invoices or preparing to start, understanding the full chain from IRP registration through GSTR-1 auto-population, ITC reconciliation, and e-way bill validity is what separates compliant operations from costly surprises.