GST on Indian invoices, practically.
A practical, no-jargon guide to GST tax invoices in India. Covers the CGST/SGST/IGST split, HSN/SAC codes, the place-of-supply rules that decide which tax applies, e-invoicing thresholds, and what every line of a compliant tax invoice should look like.
i.GST in two paragraphs
India's Goods and Services Tax (GST), introduced in July 2017, replaced a patchwork of central excise, service tax, VAT, octroi, and other indirect taxes with a unified system. GST applies to almost all supplies of goods and services. The standard structure has four main rates: 5%, 12%, 18%, and 28%. Most services land at 18%. Some goods are zero-rated, exempt, or attract a compensation cess on top of GST (luxury items, demerit goods).
Whether you charge GST depends on registration status. If you're registered (GSTIN issued), you charge GST on outward supplies, collect it from customers, claim Input Tax Credit (ITC) on your inward supplies, and remit the net to the government via monthly or quarterly returns. If you're unregistered (below the threshold) you simply don't charge GST.
ii.The registration threshold
GST registration is mandatory when your aggregate turnover crosses:
- ₹40 lakh for suppliers of goods (in most states)
- ₹20 lakh for suppliers of services (in most states)
- ₹10 lakh in special-category states (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura, Uttarakhand, Himachal Pradesh) for either goods or services
You can also register voluntarily below the threshold. Reasons to:
- Your customers are GST-registered businesses who can claim ITC on the GST you charge - so it doesn't cost them anything net.
- You can claim ITC on your business purchases (rent, software, equipment).
- Some marketplaces (Amazon, Flipkart, ONDC sellers) require GSTIN regardless of threshold.
- You appear more established to corporate clients.
Reasons not to:
- Your customers are end consumers (B2C) - adding GST to your price becomes a real cost increase.
- The compliance overhead (monthly/quarterly returns, GSTR-1, GSTR-3B, annual reconciliation) is non-trivial.
iii.CGST, SGST, IGST - which one applies?
The first question on any GST invoice is: which type of GST do I charge? The answer comes from the place of supply.
Intra-state supply
If the place of supply and the location of the supplier are in the same state, the supply is intra-state. You charge:
- CGST (Central GST) at half the total rate
- SGST (State GST) at the other half
For an 18% service supplied within Maharashtra: 9% CGST + 9% SGST = 18% total.
Inter-state supply
If the place of supply and the supplier's location are in different states (or for any export of services), you charge:
- IGST (Integrated GST) at the full rate
For an 18% service supplied by a Maharashtra-based business to a Karnataka customer: 18% IGST.
Place of supply rules - the short version
- For services to a registered (B2B) recipient: place of supply = location of the recipient
- For services to an unregistered (B2C) recipient: place of supply = location of recipient (if known/recorded) or location of supplier
- For services connected to immovable property: place of supply = location of the property
- For exports of services (recipient outside India, payment in convertible foreign exchange): treated as zero-rated supply - typically issued under LUT (Letter of Undertaking) without GST
iv.What a tax invoice must contain
Rule 46 of the CGST Rules prescribes specific fields. A valid tax invoice carries:
- Name, address, and GSTIN of the supplier
- A consecutive, unique tax invoice number (max 16 characters, alphanumeric, no gaps)
- Date of issue
- Name, address, and GSTIN of the recipient (if registered). If unregistered and supply value > ₹50,000, include name, address, and state.
- Place of supply along with state name and state code (for inter-state supplies)
- HSN code (for goods) or SAC code (for services) - see our dedicated HSN/SAC guide
- Description of goods/services, quantity (with units), and total value
- Taxable value, discount if any, and amount after discount
- Rate of tax (CGST, SGST, UTGST, IGST, cess) and amount of tax charged
- Total invoice value (in figures and words is conventional)
- Signature or digital signature of the authorised signatory
VioBusiness includes all of these by default once you set your GSTIN in the Business Profile and apply a GST rate on the invoice.
v.HSN and SAC codes
Every taxable supply must be classified under a Harmonised System Nomenclature (HSN) code for goods, or a Service Accounting Code (SAC) for services. The number of digits required depends on turnover:
- Aggregate turnover up to ₹5 crore: 4-digit HSN/SAC mandatory on B2B invoices; optional on B2C
- Aggregate turnover above ₹5 crore: 6-digit HSN/SAC mandatory on all invoices
Common SAC codes for services:
- 9983 - Other professional, technical, business services (general fallback)
- 9984 - Telecommunications and broadcasting
- 9985 - Support services
- 998313 - Information technology consulting
- 998314 - Information technology design and development
- 998361 - Advertising services
- 998722 - Photography services
See our full HSN/SAC guide for codes by profession.
vi.Invoice numbering rules
GST rules are strict about invoice numbers:
- Sequential, no gaps within a financial year
- Maximum 16 characters
- Can include letters, numbers, hyphens, or slashes
- Can reset at the start of each financial year (1 April)
- Different series allowed for different branches or document types (e.g. INV/2026-27/0001 for one series, EXP/2026-27/0001 for another)
VioBusiness's automatic numbering follows these rules. You can customise the prefix in Settings to match your preferred scheme.
vii.E-invoicing (IRP/IRN)
Above an aggregate turnover threshold, e-invoicing via the Invoice Registration Portal (IRP) is mandatory. The current threshold is ₹5 crore (rolled down progressively from earlier ₹500 crore).
Process:
- Generate the invoice with all required fields in your system.
- Upload the invoice JSON to the IRP via API or portal.
- IRP returns an Invoice Reference Number (IRN) and a QR code.
- The IRN and QR code must be printed on the physical/PDF invoice given to the customer.
- The invoice data flows automatically into your GSTR-1 return.
VioBusiness produces the underlying tax invoice PDF. For businesses required to e-invoice, the JSON from VioBusiness's exports can be uploaded to e-invoicing service providers (ClearTax, Tally, Zoho, etc.) for IRN generation. Direct IRP integration from VioBusiness is on our roadmap.
viii.Exports of services
If you supply services to a customer outside India and receive payment in convertible foreign exchange, the supply is "export of services" - a zero-rated supply under GST. Two options:
- Export with payment of IGST and refund claim: Charge IGST as if it were a regular inter-state supply, then claim a refund.
- Export under Letter of Undertaking (LUT): Issue the invoice with 0% GST, mentioning the LUT reference. No tax outflow at all.
Most freelancers and service exporters use the LUT route - it's simpler. Apply for LUT through the GST portal at the start of each financial year. Many Indian freelancers on Upwork, Fiverr, and similar platforms operate under LUT and invoice clients in USD/GBP/EUR with 0% GST. See our international invoicing guide (coming soon).
ix.How VioBusiness handles GST
Set your GSTIN once in the Business Profile. On each invoice, set the GST rate (typically 18% for services). VioBusiness automatically itemises CGST+SGST for intra-state customers or IGST for inter-state, based on the place of supply you specify. Add SAC codes per line item. The PDF carries all required tax-invoice fields. Records are stored on your phone, and CSV-exportable for your CA or GST return filing software.
For more on the app and Indian pricing, see our India page.
Disclaimer: GST law is detailed and amendments are frequent. For specific cases - composition scheme, reverse charge on specific services, branch transfers, advance receipts - consult a GST practitioner or chartered accountant.
x.Get VioBusiness
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