GST Invoice Format — Rule 46 Mandatory Fields
A missing HSN code, an unverified GSTIN, or an ambiguous place of supply can invalidate your buyer’s input tax credit. Here are the 16 mandatory particulars required under Rule 46 of the CGST Rules, with conditional requirements clearly flagged.
Under the Central Goods and Services Tax (CGST) Act, 2017, an invoice is not merely an accounting voucher or a demand for payment. It is a statutory tax document that forms the evidentiary foundation for the entire input tax credit (ITC) chain. Under Section 16(2)(a), a registered recipient cannot claim ITC unless they possess a tax invoice issued in accordance with Section 31 and Rule 46 of the CGST Rules. When an auditor or tax officer scrutinises a return, a defect in an invoice is often the fastest route to an ITC disallowance notice.
Rule 46 specifies sixteen particulars that a tax invoice issued by a registered person must contain. Notably, several of these fields are conditional upon whether the supply is B2B or B2C, whether goods or services are supplied, whether the supplier is exempt from e-invoicing, or whether delivery differs from place of supply.
The 16 mandatory particulars under Rule 46
| Clause | Field Requirement | Conditionality & Statutory Rules |
|---|---|---|
| Rule 46(a) | Name, address & GSTIN of supplier | Always mandatory. Identifies taxable entity liable to remit tax. Must match GST registration certificate. |
| Rule 46(b) | Consecutive serial number (<= 16 chars) | Always mandatory. Unique for financial year, containing only letters, numbers, hyphens, and slashes. |
| Rule 46(c) | Date of its issue | Always mandatory. Determines tax period and time of supply under Section 12 or 13. |
| Rule 46(d) | Name, address & GSTIN/UIN of recipient | Conditional: Mandatory for all B2B supplies. For unregistered recipients, omitted unless requested or under 46(e). |
| Rule 46(e) | Recipient name & address + delivery address (B2C >= ₹50,000) | Conditional: Mandatory for unregistered recipients where taxable supply is ₹50,000 or more (or where recipient requests it for < ₹50k). |
| Rule 46(f) | HSN code of goods or SAC for services | Conditional by turnover: 4 digits for AATO up to ₹5 Cr (B2B mandatory, optional B2C); 6 digits for AATO > ₹5 Cr (all supplies); 8 digits for chemical/export items. |
| Rule 46(g) | Description of goods or services | Always mandatory. Must provide an unambiguous commercial description of what was supplied. |
| Rule 46(h) | Quantity and unit | Conditional: Mandatory for supplies of goods. For service contracts billed as lump sum milestones, unit/quantity may be omitted or designated as 'nos'/'unit'. |
| Rule 46(i) | Total value of supply of goods or services | Always mandatory. The gross consideration payable prior to trade discounts. |
| Rule 46(j) | Taxable value of supply | Always mandatory. Value of supply subject to tax after deducting discounts or abatements under Section 15. |
| Rule 46(k) | Rate of tax (CGST, SGST, IGST, UTGST, Cess) | Always mandatory for taxable supplies. Specific percentage applied per line item. |
| Rule 46(l) | Amount of tax charged | Conditional: Mandatory whenever tax is chargeable. Itemised split between CGST+SGST/UTGST or IGST. Omitted on zero-rated/exempt invoices. |
| Rule 46(m) | Place of supply with State name | Conditional: Mandatory for inter-state supplies (determines IGST levy); good practice on all B2B invoices. |
| Rule 46(n) | Address of delivery (where different from POS) | Conditional: Mandatory only when the delivery destination differs from the billing place of supply. |
| Rule 46(o) | Whether reverse charge applies | Always mandatory. Explicit declaration whether recipient is liable to pay tax under Section 9(3) or 9(4). |
| Rule 46(p) | Signature / digital signature of supplier | Conditional: Mandatory for standard paper/PDF invoices. Not required if issued electronically under Rule 48(4) (e-invoicing with IRN/signed QR). |
Worked example: Inter-state IT consulting supply
Consider an independent software consultancy, "Kavita Software Studio", registered in Bengaluru, Karnataka (State Code 29, GSTIN: 29AAAAK1234A1Z5). The firm provides bespoke API engineering services to a client in Mumbai, Maharashtra, "Acro Digital Private Limited" (State Code 27, GSTIN: 27AABCA5678B1Z2). The agreed milestone billing is ₹2,50,000.
Under Section 7(1) of the IGST Act, because the location of the supplier (Karnataka) and the place of supply (Maharashtra) are in different states, this is an inter-state supply subject to Integrated Goods and Services Tax (IGST) at 18%. Charging CGST and SGST on this transaction would be a legal error; the recipient would be unable to claim ITC against their Maharashtra GSTIN.
| Invoice Section | Particulars Entered | Statutory Verification |
|---|---|---|
| Header | TAX INVOICE | Clearly distinguishes document from proforma or delivery challan. |
| Invoice Number | KSS/26-27/042 (13 chars) | Consecutive, alphanumeric, strictly <= 16 characters per Rule 46(b). |
| Invoice & Supply Date | 2026-09-28 | Issued within 30 days of service milestone completion. |
| Supplier Details | Kavita Software Studio, Koramangala, Bengaluru 560034. GSTIN: 29AAAAK1234A1Z5 | Complete legal name, physical registered address, valid GSTIN. |
| Recipient Details | Acro Digital Pvt Ltd, Bandra Kurla Complex, Mumbai 400051. GSTIN: 27AABCA5678B1Z2 | Buyer legal entity and verified GSTIN for GSTR-2B matching. |
| Place of Supply | Maharashtra (State Code: 27) | Mandatory inter-state declaration per Rule 46(m). |
| Line Item Description | Cloud architecture & API integration (SAC 998314) | Accurate 6-digit SAC code and substantive description. |
| Quantity & Rate | 1 Milestone @ ₹2,50,000.00 | Clear unit measurement and agreed milestone rate. |
| Taxable Value | ₹2,50,000.00 | Base taxable consideration. |
| Tax Split | IGST @ 18%: ₹45,000.00 (CGST: ₹0.00, SGST: ₹0.00) | Itemised tax component per Rule 46(l). |
| Total Invoice Value | ₹2,95,000.00 (Two Lakh Ninety-Five Thousand Rupees) | Total consideration payable by recipient. |
| Reverse Charge Note | Tax payable on Reverse Charge: No | Mandatory negative declaration per Rule 46(o). |
| Authorised Signatory | For Kavita Software Studio [Signed] | Authorised signature per Rule 46(p). |
Mandatory e-invoicing: Current turnover thresholds
Since its staggered rollout, electronic invoicing (e-invoicing) has transformed B2B compliance in India. Under Rule 48(4) of the CGST Rules, an e-invoice is not an invoice created as a PDF or emailed to a client; it is an invoice whose schema has been uploaded to and validated by an Invoice Registration Portal (IRP), which issues a unique 64-character Invoice Reference Number (IRN) and a digitally signed QR code.
Pursuant to Notification No. 10/2023–Central Tax (effective 1 August 2023), mandatory e-invoicing applies to any registered business whose Aggregate Annual Turnover (AATO) exceeds ₹5 Crore in any preceding financial year from 2017–18 onwards. Turnover is calculated at the entity-wide PAN level across all states. If your aggregate turnover crossed ₹5 Crore in FY 2022–23 or any subsequent year, every B2B invoice, credit note, debit note, and export invoice must carry an IRN and IRP-signed QR code. Generating a standard paper or non-IRN invoice when mandated by law renders the invoice void under Rule 48(5), and your customer will be denied ITC.
Common GST invoice errors that trigger scrutiny
- Exceeding the 16-character limit: Adding prefixes like "COMPANYNAME/INVOICE/2026-27/001" breaks Rule 46(b) and causes errors when uploading to the GST portal.
- Mismatched Place of Supply: Charging CGST+SGST when the place of supply is outside your state forces your client to reject the invoice, as CGST cannot be offset across state lines.
- Truncated HSN/SAC codes: Businesses with turnover above ₹5 Crore must quote 6-digit HSN/SAC codes for B2B supplies; using 2 or 4 digits invites audit queries.
- Omitting the reverse charge declaration: Leaving the RCM field blank rather than explicitly declaring "No" is a technical defect frequently cited in scrutiny notices.
Disclaimer: Invoicr formats tax invoices according to statutory templates. This article provides general educational information under Indian GST law, not formal tax or legal advice. Verify complex place-of-supply classifications with your chartered accountant.
Invoicr validates structure and arithmetic, not your business facts. This is general information, not tax, accounting or legal advice — check anything consequential with your accountant.