How to generate a GST invoice (with HSN, e-invoice, and 2026 rules)

A GST invoice is the single most important document an Indian business issues. Get it wrong and you lose Input Tax Credit, face audit notices, and create disputes. Here is the exact format.

Step 1: Include all mandatory fields

Supplier GSTIN, name, address. Recipient GSTIN (if registered), name, address. Invoice number (sequential, unique per FY). Invoice date. Place of supply with state code. HSN/SAC code per item. Description. Quantity, unit, rate. Taxable value. CGST, SGST, IGST or UTGST rates and amounts. Total invoice value (number AND words).

Step 2: Pick the right tax category

Intra-state supply → CGST + SGST. Inter-state supply → IGST. Export → zero-rated (or with bond/LUT). Reverse-charge transactions need 'Reverse charge applicable' on the invoice.

Step 3: Get the HSN code right

Goods → HSN code (4 digits if turnover < ₹5 cr, 6 digits if above). Services → SAC code (starts with 99). Use the free HSN code finder at indiacrm.in/tools/hsn-code-finder. Wrong HSN = wrong GST rate = audit.

Step 4: Generate the IRN if applicable

If your turnover exceeded ₹5 cr in any FY since 2017-18, e-invoicing is mandatory. Upload the invoice to einvoice1.gst.gov.in or use a GSP. Get back the IRN (Invoice Reference Number) and signed QR code, embed both on the invoice.

Step 5: Issue within the right timeline

For goods → at the time of removal (movable goods) or delivery (immovable goods). For services → within 30 days of supply (45 days for banking/insurance/telecom). Late issuance ≠ invalid, but creates audit risk.

Step 6: Keep digital copies for 6 years

Section 36 of CGST Act requires 6-year retention. Cloud storage with timestamp is acceptable. Lost invoices = denied ITC during scrutiny.

Frequently asked questions