GST Invoice Guide for Small Business Owners India 2026
By Sneha Patel, CA · · 13 min read
Creating a GST-compliant invoice is not optional for registered businesses in India — it is a legal requirement. An incorrect or incomplete invoice can result in your customer being unable to claim Input Tax Credit (ITC), damaging your business relationships.
Mandatory Fields on Every GST Invoice
- Supplier's GSTIN (GST Identification Number)
- Invoice number and date (sequential, no gaps in numbering)
- Recipient's name, address, and GSTIN (for B2B)
- Description of goods/services
- HSN (goods) or SAC (services) code
- Quantity and unit of measurement
- Total value before tax
- Applicable tax rate and amount (CGST + SGST for intra-state, IGST for inter-state)
- Total invoice value (including taxes)
- Signature or digital signature
E-Invoicing Requirements
As of 2024, businesses with annual turnover above ₹5 crore must use the Government's e-Invoice system (IRP portal). Invoices are validated by the portal and an IRN (Invoice Reference Number) is issued. The QR code on e-invoices must be generated by the IRP portal — not manually.
Common GST Invoice Mistakes
- Missing HSN/SAC codes (mandatory for all B2B invoices)
- Incorrectly splitting CGST/SGST vs. IGST (inter-state vs. intra-state error)
- Invoice numbering gaps or restarts
- Collecting GST before GST registration
Use DigiNow's GST Calculator to verify your tax amounts before sending invoices.