Every GST invoice must include 16 mandatory fields. Missing even one can block your customer's input tax credit. Here is the complete format with rules, examples, and free templates.
A GST invoice is not just a bill — it is a legal document that determines input tax credit for your customer. If your invoice is missing mandatory fields or has wrong information, your customer cannot claim ITC on that purchase. This costs them real money and strains business relationships.
Under Section 31 of the CGST Act, every registered person making a taxable supply must issue a tax invoice. The format and content requirements are specified in Rule 46 of the CGST Rules. These rules apply to every business — whether you sell products, provide services, or do both.
After the GST 2.0 reform in September 2025, the invoice format itself has not changed. But the tax rates on your invoices have — the 12% and 28% slabs no longer exist, replaced by 5%, 18%, and the new 40% luxury slab. Make sure your invoicing software reflects the new GST rates.
This guide covers every mandatory field, common format mistakes, B2B vs B2C invoice differences, and how to create compliant invoices quickly. Use our free invoice generator to create a GST-compliant invoice right now, or browse invoice format templates for different industries.
Every tax invoice must include all of these — as per Rule 46 of CGST Rules
The format changes based on whether your customer is GST-registered
| Feature | B2B Invoice | B2C Invoice |
|---|---|---|
| Customer GSTIN | Mandatory | Not required |
| Place of Supply | Mandatory | Mandatory only for inter-state > Rs 2.5L |
| HSN Code | 4 or 6 digits required | 4 or 6 digits required |
| Tax Breakup | CGST+SGST or IGST line-wise | CGST+SGST or IGST (can be consolidated) |
| Invoice Serial | Unique, sequential | Unique, sequential |
| Reported in GSTR-1 | Table 4 — invoice-wise | Table 5 (Large) or Table 7 (Small) |
| ITC for customer | Customer can claim ITC | No ITC — consumer is end user |
| E-invoice | Required if turnover > Rs 5 crore | Not required |
The invoice number is one of the most commonly botched fields. Here are the rules from Rule 46 of CGST Rules:
Sequential: Invoice numbers must be in a consecutive serial order. You cannot skip numbers or reuse them. If you issue invoice MBP-001, the next must be MBP-002, not MBP-005.
Maximum 16 characters: The invoice number cannot exceed 16 characters including any prefix. Characters allowed are alphanumeric, dash (-), and forward slash (/) only. No spaces, dots, or other special characters.
Financial year reset: You can reset the series at the start of each financial year. Common format: MBP/2026-27/001 for FY 2026-27. Make sure the total stays within 16 characters.
Multiple series: A business can maintain multiple invoice series — for example, one for sales (INV-001) and one for exports (EXP-001). Each series must be independently sequential.
No amendments to invoice number: Once issued, an invoice number cannot be changed. If there is an error, issue a credit note and create a new invoice with the next available number.
In myBillPlease, invoice numbers auto-increment following your configured series. You set the prefix and starting number once — the system handles sequential numbering automatically.
HSN codes are mandatory on every GST invoice. The number of digits required depends on your annual turnover:
Turnover up to Rs 5 crore: 4-digit HSN code required on invoices. Example: 6109 for T-shirts.
Turnover above Rs 5 crore: 6-digit HSN code required. Example: 610910 for T-shirts of cotton.
Exports and imports: 8-digit HSN code required. Example: 61091010 for T-shirts of cotton, knitted.
Using the wrong HSN code or omitting it attracts a penalty of Rs 50 per invoice under Section 125 of the CGST Act, up to a maximum of Rs 25,000 per financial year. This adds up fast if you issue hundreds of invoices per month.
Find the correct HSN code for any product using our HSN code directory — all 97 chapters with 22,000+ codes searchable by name or number. Or use the HSN code finder tool for quick lookups.
Avoid these errors that cause ITC rejection and GST notices
For B2B invoices, customer GSTIN is mandatory. Without it, the invoice is treated as B2C and your customer cannot claim ITC. Always collect and verify GSTIN before invoicing.
The state code determines IGST vs CGST+SGST split. Wrong state code means wrong tax calculation. State code comes from the first 2 digits of GSTIN — verify it matches the delivery address.
GST must be shown as a separate line — CGST and SGST for intra-state, or IGST for inter-state. Showing a lump-sum amount without tax breakup makes the invoice non-compliant.
Invoice date should be the date of issue. For goods, it must be issued before or at the time of removal. For services, within 30 days of supply completion. Backdating invoices is illegal.
Invoice numbers longer than 16 characters or containing invalid characters get rejected on the GST portal. Keep your prefix short and let the system handle numbering.
Place of Supply is mandatory for all B2B invoices and for inter-state B2C invoices above Rs 2.5 lakh. Missing it causes classification errors in GSTR-1 filing.
You have two options for creating proper GST invoices:
Option 1: Use our free invoice generator. Visit mybillplease.com/tools/invoice-generator, fill in your details, add items with HSN codes, and download a professional PDF invoice. No signup required. Works for one-off invoices or when you need a quick bill.
Option 2: Use myBillPlease for ongoing billing. Sign up free, add your products with HSN codes and GST rates once, and create invoices in 30 seconds every time. Customer details auto-fill, tax calculates automatically, invoice numbers auto-increment, and your GSTR-1 report generates from all your invoices at month-end. Choose from 7 professional PDF templates.
Both options ensure your invoices include all 16 mandatory fields. The free plan has no invoice limit and no expiry — use it as long as you need.
All 16 mandatory fields included automatically. 7 professional templates. Auto-calculated tax. No credit card needed.
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