Whether you're setting up billing software for the first time or you're the accounting guru your team relies on, this guide gives you the complete picture of GST-compliant billing in India — from mandatory invoice fields to advanced automation tips.
GST Invoice Mandatory Fields (2025)
A GST invoice must include all of the following — missing any one can make it legally invalid:
| Field | Required For |
|---|---|
| Supplier's Name, Address & GSTIN | All GST invoices |
| Invoice Number (unique serial) | All GST invoices |
| Date of Issue | All GST invoices |
| Recipient's Name, Address & GSTIN | B2B transactions |
| Place of Supply | All GST invoices |
| HSN/SAC Code | Goods & Services |
| Quantity and Unit | Goods |
| Total Value & Taxable Value | All GST invoices |
| CGST + SGST / IGST Amount | All GST invoices |
| Signature (digital or physical) | All GST invoices |
From April 2023, businesses with annual turnover above ₹5 crore must generate e-invoices (IRN + QR code) for every B2B sale. Your billing software must support direct IRP integration for this.
Common GST Billing Mistakes to Avoid
- Wrong HSN code — Each product category has a specific HSN code with its own tax rate. Using the wrong HSN can mean under- or over-charging tax.
- Mismatched Place of Supply — If the customer is in a different state, you charge IGST (not CGST+SGST). Getting this wrong creates tax liability.
- Missing GSTIN on B2B invoices — Your B2B customer can't claim input tax credit without your GSTIN on the invoice.
- Wrong invoice date — Invoice date triggers the tax payment due date. Future-dating invoices is illegal.
- Not reconciling with GSTR-2B — If your purchase invoices don't match your supplier's GSTR-1 filings, your ITC claim will be blocked.
GSTR-1 vs GSTR-3B: What Your Software Should Help With
GSTR-1 reports all your outward sales (invoices issued). Filed monthly or quarterly. Your billing software should auto-populate this from your invoices.
GSTR-3B is your summary return where you declare tax liability and claim ITC. Filed monthly. Your billing software should give you a ready GSTR-3B summary to verify before filing on the GST portal.
Automating Your Monthly Tax Routine
A good billing software should reduce your monthly GST filing to under 30 minutes:
- All sales auto-captured from POS and invoice module
- GSTR-1 report generated in one click (JSON or Excel format)
- GSTR-3B summary pre-calculated
- ITC from purchases auto-reconciled
- Export to GST portal or send to CA via email
Expert Checklist: Before You Choose Any Billing Software
- ✅ Does it support all GST invoice formats (B2B, B2C, export)?
- ✅ Can it generate GSTR-1 export (JSON format)?
- ✅ Does it handle e-invoicing (IRN generation)?
- ✅ Is data encrypted and automatically backed up?
- ✅ Is there phone/WhatsApp support in Indian business hours?
- ✅ Can you try it free before paying?
Billux checks every box on this list. Start your expert-level billing with a free 15-day trial at billux.in/register.
