If you are registered under GST, every sale to a customer needs a proper tax invoice. A missing GSTIN or wrong tax split can create trouble for your buyer's input tax credit — and for you during a notice or audit.
This is a practical checklist, not legal advice. Always confirm current rules with your CA or the official GST portal.
Fields a GST Tax Invoice Should Contain
- Your details: business name, address and GSTIN
- Invoice number: a unique, consecutive serial number for the financial year (for example AIV-2026-001)
- Invoice date
- Customer details: name, address, and GSTIN if the customer is registered
- Place of supply (state) — this decides CGST+SGST or IGST
- Description of goods/services with HSN or SAC code
- Quantity, unit and rate
- Taxable value (after discount)
- Tax rate and amount — CGST + SGST for intra-state, IGST for inter-state
- Total invoice value in figures (and preferably in words)
- Signature or digital signature of the supplier
CGST + SGST or IGST?
| Situation | Tax to charge |
|---|---|
| Seller and buyer in the same state | CGST + SGST (rate split half-half, e.g. 9% + 9% for 18%) |
| Seller and buyer in different states | IGST (full rate, e.g. 18%) |
| Export | Zero-rated (with LUT/bond as applicable) |
Common Invoice Mistakes
- Breaking the number sequence or reusing numbers across years
- Charging IGST on a local sale (or CGST+SGST on an inter-state sale)
- Missing HSN/SAC codes
- Wrong customer GSTIN — your buyer may lose input tax credit
- No backup — invoices kept only on one laptop that later crashes
The Easy Way: an Offline Invoice Generator
Writing invoices in Word or Excel by hand leads to exactly these mistakes. AIVEXA's Invoice Generator Pro is a one-time-purchase tool that works 100% offline in your browser:
- GST-ready: intra-state (CGST+SGST) and inter-state (IGST)
- Auto-incrementing bill numbers with your own prefix
- Your logo, 8 colour themes, notes and payment terms
- Invoice history, auto-save, and JSON backup/restore
- One-click print that fits A4 — no subscription, no cloud
If you also want free calculators, try the GST Calculator on AIVEXA.
