The complete guide to GST invoicing in India (2026 edition)

Under the CGST Act, an "invoice" or "tax invoice" is a document issued by a supplier of taxable goods or services to a recipient, containing the prescribed particulars set out in Rule 46 of the CGST Rules. It is the trigger for the supplier's tax liability under the time-of-supply provisions in Sec 12 and Sec 13, and it is the source document the recipient relies on to claim Input Tax Credit under Sec 16. Issue it wrong and both ends of the chain break.

The economic and legal weight of an invoice in GST is heavier than under the pre-GST regime. Pre-2017, an invoice issued under VAT or Service Tax was largely an internal book-keeping artefact; the buyer's credit was decided independently of whether the seller had even raised an invoice. Under GST, the invoice flows from supplier to recipient through the GSTN — first via GSTR-1, then auto-populating GSTR-2B, then enabling the recipient's GSTR-3B credit. The invoice is the unit of compliance; getting the data right is the whole game.

1.1 The 16 mandatory fields of Rule 46

1. Name, address, and GSTIN of the supplier.
2. A consecutive serial number, not exceeding 16 characters, in one or multiple series, containing alphabets, numerals, and special characters (hyphen and slash only), unique for a financial year.
3. Date of issue.
4. Name, address, and GSTIN of the recipient (if registered).
5. Where the recipient is unregistered and the value is ≥ ₹50,000: name and address of the recipient and the address of delivery, with the state name and code.
6. HSN code for goods or SAC for services (digits depend on turnover; see §1.2).
7. Description of goods or services.
8. Quantity and unit (Unique Quantity Code — UQC).
9. Total value.
10. Taxable value (after discount or abatement).
11. Rate of tax (CGST / SGST / IGST / cess).
12. Amount of tax charged (CGST / SGST / IGST / cess).
13. Place of supply with state name, for inter-state supplies.
14. Address of delivery, if different from the place of supply.
15. Whether the tax is payable on reverse charge basis.
16. Signature or digital signature of the supplier or an authorised representative.

For e-invoices, fields 2, 3, and the QR code are auto-populated by the IRP — the IRN goes on the printed copy along with the QR code carrying the cryptographically signed invoice data.

1.2 HSN / SAC digit requirements

The HSN/SAC code on a line item drives the GST rate. Wrong HSN typically produces the wrong tax — and the wrong tax recovered from the customer is recovered with interest, even if the rate was honest error. The IRP's HSN validity check (since 1 Oct 2023) rejects invoices with HSN codes not in the official master, which has dramatically reduced typos.

1.3 When the invoice must be issued

• Goods, movement involved (Sec 31(1)(a)) — before or at the time of removal for supply.
• Goods, no movement (Sec 31(1)(b)) — before or at the time of delivery / making available.
• Continuous supply of goods (Sec 31(4)) — on or before the date of each statement of account or each payment, whichever is earlier.
• Services — general (Sec 31(2) + Rule 47) — within 30 days of supply (45 for insurer, banking company, financial institution including NBFC, telecom).
• Continuous supply of services (Sec 31(5)) — on or before the due date of payment if ascertainable from the contract; on or before receipt of payment otherwise; on or before completion of the event if payment is linked to it.
• Goods sent on approval (Sec 31(7)) — before or at the time of supply or 6 months from removal, whichever is earlier.

A worked example is worth ten paragraphs of regulation. Below is a clean tax invoice for an inter-state B2B supply of services from a Maharashtra-based consulting firm to a Delhi-headquartered company:

Acme Consulting LLP                                  Tax Invoice
501, Phoenix Marketcity, LBS Marg                     Original for Recipient
Kurla West, Mumbai 400070
GSTIN: 27ABCDE1234F1Z5                                Invoice No: AC/26-27/00041
PAN: ABCDE1234F                                       Invoice Date: 14 May 2026
State / Code: Maharashtra / 27                        Place of Supply: Delhi (07)
                                                       Reverse Charge: No

Bill To:                                              Ship To: (same)
Beta Industries Pvt Ltd
2nd Floor, Tower B, Cyber Hub
DLF Cyber City, Gurugram (well actually Delhi office)
GSTIN: 07PQRST5678K2Z9
State / Code: Delhi / 07

S No  Description                       SAC     Qty   Rate     Taxable
                                                                Value
1     Q4 advisory services —            998311  1     250,000   250,000
      growth strategy retainer
2     Workshop facilitation —           998311  2      75,000   150,000
      board offsite, two days

                                          Sub-total                 400,000
                                          Discount                       –
                                          Taxable value             400,000
                                          IGST @ 18%                 72,000
                                          ───────────────────────────────
                                          INVOICE TOTAL             472,000
                                          (Rupees Four Lakh Seventy
                                          Two Thousand only)

Amount in words:    INR Four Lakh Seventy Two Thousand only
Payment terms:      NEFT/RTGS to HDFC, A/c 50100123456789, IFSC HDFC0001234
Authorised signatory:  (digitally signed)
IRN: 35a17cb87a6e... (64 chars)                       [QR Code]
Acknowledgement No: 2026051400123456                  IRP signed: 14 May 2026 14:32 IST

Three details on this invoice that frequently get botched in the wild:

• Place of Supply is Delhi (07), not Gurugram (Haryana). The recipient's GSTIN starts with 07, so the registered place is Delhi. Even though the work was performed at a Gurugram office, the default for B2B services (Sec 12(2)) is the location of the recipient's registered office. IGST applies because PoS (07) ≠ Supplier State (27).
• IGST is shown as a single line of ₹72,000. There is no CGST/SGST split because the supply is inter-state. Splitting it into CGST + SGST on an inter-state supply blocks ITC for the recipient.
• IRN and QR are mandatory for this supplier (Acme Consulting at ₹5cr+ turnover). The IRN goes on the visible portion of the invoice — not in the footer in 6pt grey font.

2.1 Number of copies

Rule 48 prescribes: goods — triplicate (original for recipient, duplicate for transporter, triplicate for supplier); services — duplicate (original for recipient, duplicate for supplier). The copies must be marked accordingly. Electronic invoices satisfy this requirement; printing one paper copy for the recipient is enough.

2.2 Invoice numbering — practical rules

The 16-character limit, "alphanumeric with hyphens and slashes", and "consecutive serial number unique per FY" combine into a small set of compliant patterns:

• Reset the series on 1 April every year — running a continuous series across FYs is allowed but a fresh series per FY makes audit cleaner.
• You can run multiple series in the same FY (one per branch, one per business vertical), each separately consecutive. Document the series in your books so an auditor can verify completeness.
• Never re-use a serial number within an FY — even if the original invoice was cancelled and recreated.
• For e-invoices, the IRP enforces uniqueness across the entire FY for the supplier's GSTIN. Re-use returns an error.

E-invoicing rolled out in phases. The threshold was ₹500 crore in October 2020, dropped to ₹100 crore in January 2021, ₹50 crore in April 2021, ₹20 crore in April 2022, ₹10 crore in October 2022, and ₹5 crore in August 2023. The threshold is sticky: once your aggregate turnover crosses ₹5 crore in any preceding FY since 2017-18, you are in scope from the first day of the next FY onwards — and stay in scope even if turnover later drops below ₹5 crore.

3.1 What is in and out of scope

In scope (must e-invoice):

• B2B tax invoices.
• B2G (supplies to government entities / SEZ Units).
• Export invoices (with or without IGST).
• Credit notes and debit notes against any of the above.

Out of scope (e-invoice not required):

• B2C invoices (but B2C QR is required separately for AATO > ₹500 crore — Rule 46A).
• Bills of supply (composition or exempt supplies).
• Self-invoices under reverse charge.
• Delivery challans, non-GST documents.
• Specified entity categories (SEZ Units, banks, NBFCs, GTA, passenger transport, cinema admission, government departments).

3.2 IRP workflow, end to end

1. Build the invoice JSON in INV-01 schema (currently v1.1, JSON spec at einvoice1.gst.gov.in).
2. POST to the IRP via API. Six IRPs are operational; pick one in your config — failover between IRPs is supported.
3. The IRP validates business rules: GSTIN active, recipient state code matches GSTIN, taxable value sums to total, IGST vs CGST+SGST chosen correctly given PoS, HSN exists in master, invoice date within window.
4. On success, the IRP returns: IRN (SHA-256 hash of supplier-GSTIN + supplier-invoice-no + FY + doc-type), QR code (base64 PNG), acknowledgement number, signed JSON.
5. Print the QR code and IRN on the customer-facing invoice. The signed JSON should be archived for at least 6 years per Sec 36.

3.3 The 30-day rule

From 1 November 2023, taxpayers with AATO ≥ ₹10 crore must obtain the IRN within 30 days of invoice date (GSTN advisory). The IRP rejects late submissions. Operationally this kills back-dated invoicing — you cannot raise a 1 April invoice on 15 May. Build invoice issuance into the same workflow as the customer-facing PDF; do not queue invoices for monthly batch processing.

3.4 Cancellation, amendment, and the 24-hour window

E-invoices can be cancelled on the IRP within 24 hours of generation, end-to-end. Beyond 24 hours the IRP does not allow cancellation — corrections must go via credit notes (each itself an e-invoice). Amendments to specific fields (other than full cancellation) must be done on the GST portal at the GSTR-1 stage; the IRP does not support partial amendments.

3.5 B2C QR (Notification 14/2020-CT)

Separate from B2B e-invoicing, businesses with AATO > ₹500 crore must print a dynamic QR code on B2C invoices that allows the customer to scan and pay. The QR encodes the supplier's UPI VPA, invoice number, value, and a checksum. Non-compliance attracts penalty under Sec 125.

A tax invoice (Sec 31, Rule 46) is issued for taxable supplies. It shows the GST rate and amount, and the recipient (if registered) claims ITC against it.

A bill of supply (Sec 31(3)(c), Rule 49) is issued in two situations: (a) the supplier is a composition taxpayer; or (b) the supplier is making exempt supplies. No GST is shown on a bill of supply, and the recipient has no ITC.

4.1 Mandatory fields for a Bill of Supply

Rule 49 mirrors Rule 46 minus the tax fields:

1. Name, address, GSTIN of the supplier.
2. Consecutive serial number (≤ 16 chars), unique per FY.
3. Date.
4. Name, address, GSTIN (if registered) of the recipient.
5. HSN / SAC.
6. Description.
7. Value.
8. Signature or digital signature.

Composition dealers must include the text "Composition taxable person, not eligible to collect tax on supplies" prominently. Exempt suppliers do not need the composition text but must indicate the exemption notification reference.

4.2 Single-document combined invoice (Rule 46A)

When a registered person supplies both taxable and exempt items to an unregistered recipient on the same transaction, a single "invoice-cum-bill of supply" can be issued under Rule 46A — with taxable lines carrying GST and exempt lines without. Retail-end businesses use this most.

A credit note (Sec 34(1)) is issued by a supplier to a recipient when the taxable value or tax on the original invoice was higher than the actual value/tax — typically for sales returns, post-supply discounts (if linked to the invoice), or rate revisions downward. It reduces the supplier's GST liability.

A debit note (Sec 34(3)) is issued when the taxable value or tax on the original invoice was lower than the actual — typically for upward rate revisions, undercharged GST, or post-supply price escalations. It increases the supplier's GST liability.

5.1 Time limit for credit notes

Sec 34(2): a credit note must be declared in the GSTR-1 of the month of issue or before 30 November of the following FY or the date of the annual return for that FY, whichever is earlier. After that, the credit note no longer reduces GST liability — you can still issue it commercially, but the GST you collected on the original invoice is not refunded.

Debit notes have no equivalent time limit — the supplier is increasing liability, so the government has no objection to a late declaration. Interest under Sec 50 applies to the additional tax.

5.2 Fields required (Rule 53)

1. Word "Revised Invoice" or "Supplementary Invoice" or "Credit Note" / "Debit Note" prominently.
2. Name, address, GSTIN of supplier.
3. Document number (serial, ≤16 chars, unique).
4. Date.
5. Name, address, GSTIN of recipient.
6. Serial number and date of the original invoice.
7. Value of the adjustment.
8. Rate and amount of tax adjustment.
9. Signature.

5.3 E-invoicing applies to credit/debit notes

For taxpayers in scope of e-invoicing, every credit and debit note linked to a B2B/SEZ/export invoice must itself carry an IRN. The IRP allows a credit note linked to an invoice that was itself e-invoiced. Linking to a non-e-invoiced original is rejected — which is why e-invoicing adopters must process the cleanup of pre-threshold invoices through commercial credit notes only.

An export invoice is a tax invoice issued for an export of goods or services. Exports are zero-rated supplies under Sec 16 of the IGST Act, which gives the exporter two refund routes:

1. Export with payment of IGST — charge IGST on the export invoice at the applicable rate, pay it in cash through GSTR-3B, and claim the IGST back via the auto-refund route. The shipping bill itself is the refund application; ICEGATE shares data with GSTN; refund is credited to the exporter's bank.
2. Export under Letter of Undertaking — file LUT in RFD-11 (annual, online, no documents needed beyond the form itself), don't charge IGST on the export invoice (zero-rated supply zero), and claim refund of unutilised ITC through RFD-01.

LUT is the default choice for most exporters because it preserves working capital — you never pay IGST that you'll wait 60 days to get back. With-payment is occasionally preferred by exporters with a strong domestic output liability who use IGST credit accumulation as a buffer.

6.1 Export invoice — additional fields

Rule 46 lists three extra fields for export invoices: (a) endorsement reading "Supply meant for export on payment of IGST" or "Supply meant for export under bond or Letter of Undertaking without payment of IGST"; (b) name and address of the recipient (no GSTIN — the recipient is overseas); (c) name of the country of destination and the delivery address there.

The shipping bill number, port code, and date must be entered against each export invoice in GSTR-1's Table 6A — the linkage is what unlocks the auto-refund.

6.2 Currency, conversion and forex rules

Export invoices can be denominated in foreign currency. For GST reporting, convert to INR using the rate notified by the CBIC (CBIC publishes weekly exchange rates under Section 14 of the Customs Act). Banks treat the FIRC (Foreign Inward Remittance Certificate) or e-BRC as proof of realisation; without realisation in the period prescribed (typically 9 months from the date of export, extendable), the export is not "zero-rated" and IGST becomes payable.

6.3 Export of services — the five conditions

Export of services is zero-rated only if all five conditions in Sec 2(6) IGST Act are met:

1. Supplier is located in India.
2. Recipient is located outside India.
3. Place of supply is outside India.
4. Payment is received in convertible foreign exchange (or INR where permitted by RBI).
5. Supplier and recipient are not merely establishments of a distinct person under Explanation 1 to Sec 8 (i.e., not the same legal entity).

Failure on any of the five drops the supply out of zero-rated; the supplier becomes liable to GST as if it were a normal supply. The fifth condition is the trap — a wholly owned Indian subsidiary providing services to its overseas parent is a distinct person (different legal entities), so the supply does qualify; but a branch office providing services to its head office is the same legal entity and the supply does not qualify.

Supplies to a Special Economic Zone Unit or SEZ Developer are zero-rated under Sec 16(1)(b) IGST Act. They have the same two refund routes as exports — with IGST and refund, or under LUT without IGST.

7.1 SEZ endorsement

Unlike a physical export, the goods do not leave India — they enter the SEZ. Proof of supply is the SEZ recipient's endorsement on the invoice (and, for goods, the gate pass on the bill of entry). Without this endorsement, the refund route does not unlock. SEZ developers and units have a specified officer who endorses the documents; build the endorsement step into your fulfilment workflow.

7.2 SEZ invoice — fields

The invoice carries the SEZ Unit's GSTIN (yes, SEZ Units have GSTINs and they appear as "SEZ" in the GST master). The endorsement reads "Supply meant for SEZ Unit / Developer under bond / LUT without payment of IGST" or "Supply meant for SEZ Unit / Developer on payment of IGST".

The supplier's GSTR-1 captures SEZ supplies in Table 6B (with IGST) and Table 6C (without IGST under LUT). The supplier files a refund claim via RFD-01 with the endorsed invoices as supporting documents.

7.3 E-invoicing for SEZ Developers but not Units

A quirk of the rules: SEZ Developers are required to e-invoice (if they cross the threshold), but SEZ Units are exempt. This is because Units consume in the zone and don't typically issue B2B outward supplies to the DTA (Domestic Tariff Area); when they do, those supplies follow normal e-invoicing if the Unit is in scope by turnover — but the default is exemption.

Reverse Charge Mechanism (RCM) reverses the normal flow — the recipient pays the GST instead of the supplier. RCM applies in two situations:

• Sec 9(3) — specified categories of supply notified by the government. The current Notification 13/2017-CT(R) and 10/2017-IGST(R) list ~17 categories: GTA (subject to forward-charge option), legal services from advocates and law firms, services by an arbitral tribunal, sponsorship services, services by directors to companies, insurance agent services, recovery agent services, copyright services, security services from a non-body-corporate, renting of motor vehicles in specified scenarios.
• Sec 9(4) — supplies received by a registered person from an unregistered person. Currently restricted to notified classes — primarily real-estate promoters per Notification 7/2019-CT(R).

8.1 When the supplier is registered

The supplier still issues a tax invoice under Rule 46. The invoice shows the GST rate (e.g., 18%) but does not collect tax — instead it carries the prominent note "Tax payable on reverse charge basis" and "TAX TO BE PAID BY RECIPIENT". The recipient pays the GST in cash through GSTR-3B Table 3.1(d). Once paid, the recipient can claim ITC in the same return (subject to standard Sec 16 conditions and not blocked under Sec 17(5)).

8.2 When the supplier is unregistered

The supplier cannot issue a tax invoice (they are unregistered). The recipient — Sec 31(3)(f) — issues a self-invoice in the same format as a normal tax invoice but with the recipient's own GSTIN as the supplier-side details and the unregistered party's details as the recipient (the polarity is reversed for documentation purposes). The recipient also issues a payment voucher under Sec 31(3)(g) when making payment.

Self-invoicing and payment voucher are due dates worth tracking: self-invoice on or before the receipt of goods/services; payment voucher on payment.

8.3 RCM ITC mechanics

GST paid under RCM cannot be paid by ITC offset — it must be paid in cash. Once paid, the same amount is available as ITC subject to Sec 16. The cash and credit happen in the same GSTR-3B: pay through Table 3.1(d) in cash; claim through Table 4A(3) as ITC.

Rule 46 requires a "signature or digital signature of the supplier or his authorised representative". Both are valid; nothing in the rules mandates a digital signature for paper invoices. In practice, the requirement is satisfied as follows:

• Paper invoices — a manual signature in ink. Pre-printed signature ("Authorised signatory" with an image) is generally accepted by courts as compliance.
• Electronic invoices, non-e-invoiced — DSC of the authorised signatory or an electronic signature recognised under the IT Act 2000.
• E-invoices (IRP-signed) — the IRP signs the JSON with its own DSC and embeds a signed QR. The supplier's DSC is not separately required. The IRP signature is recognised under the IT Act as a valid digital signature.

9.1 DSC for the GST portal

Filing GST returns from the portal requires either DSC (Class 2 or 3, individual or organisational) or EVC (Aadhaar OTP-based). Companies and LLPs must use DSC; proprietorships and partnerships have the EVC option. DSCs from any of the seven licensed Certifying Authorities (e-Mudhra, Sify, NSDL, Capricorn, Verasys, IDSign, ProDigiSign) are accepted.

9.2 Invoice archiving and Sec 36

Sec 36 of the CGST Act requires every registered person to maintain books of account and all invoices, credit/debit notes, bills of supply and delivery challans for at least 72 months from the due date of the annual return for the relevant FY. For FY 2025-26 that's 6 years from 31 December 2026. Electronic copies (including the signed JSON of e-invoices) satisfy the rule under Rule 56(15).