GST Invoice Format Guide for Small Businesses in India (Free Template Included)

For a B2B transaction, an incorrectly formatted GST invoice isn't just an administrative annoyance — it can cause the client's input tax credit (ITC) claim to be rejected, which means they end up paying tax twice on the same transaction. That's the kind of mistake that damages a client relationship far more than its size suggests.

The good news is that the mandatory fields are well-defined and don't change transaction to transaction. Once a business has its invoice template configured correctly, every subsequent invoice is correct by default. The risk is almost entirely in the initial setup — getting it right once.

• Invoice number — a unique, sequential number for the financial year (e.g., INV-2026-0001). It cannot be reused and should follow a consistent series.

• Invoice date — the date of issue.

• Supplier details — your legal business name, address, and GSTIN.

• Recipient details — the client's name, address, and GSTIN (mandatory for B2B; for B2C transactions under ₹50,000 it can be omitted, but including it is good practice if available).

• HSN/SAC code — the Harmonised System of Nomenclature code for goods, or Services Accounting Code for services, identifying exactly what is being billed.

Description, quantity, and unit price of each line item.

• Taxable value — the value before tax, per line item.

• Tax breakdown — CGST + SGST shown separately for intra-state transactions, or IGST alone for inter-state transactions. Never combine them into a single "GST" line.

• Place of supply — the state where the transaction is deemed to occur, which determines whether CGST+SGST or IGST applies.

Total invoice value, including tax, in figures.

• Signature — physical or digital, of the supplier or an authorised representative.

This is the single most common GST invoicing mistake for small businesses. The rule is straightforward but easy to get backwards under deadline pressure:

Intra-state transaction (supplier and place of supply in the same state): charge CGST (9%) + SGST (9%) for an 18% GST rate, shown as two separate line items.

Inter-state transaction (supplier and place of supply in different states): charge IGST (18%) as a single line item. Never split inter-state tax into CGST+SGST.

The "place of supply" is what determines this — not where your office happens to be, but where the service or goods are deemed delivered, which for most B2B services is the client's registered address. Get the client's state right and the CGST/SGST-vs-IGST split follows automatically.

Every line item needs an HSN code (goods) or SAC code (services) — a standardised classification that tells the tax authority exactly what was sold. Using the wrong code, or a generic placeholder, is a common audit flag.

For services-based businesses — agencies, consultants, SaaS companies — the relevant SAC codes are published by the CBIC and are searchable by service category. Once you've identified the correct code for your core service line, it stays the same on every invoice you issue for that service — set it once in your invoicing tool and it should auto-apply going forward rather than being typed manually each time.

Most small businesses that try to build a GST-compliant invoice in Word or Excel make one of two mistakes: they format it correctly once, then forget to update the sequential invoice number correctly the next month, or they manually calculate CGST/SGST and get the split wrong on an inter-state transaction.

A dedicated invoicing tool removes both risks — the invoice number increments automatically, and the CGST/SGST-vs-IGST split is calculated from the client's state rather than typed in manually. DeskPanda's invoice builder is GST-compliant by default: set your GSTIN and tax configuration once, and every invoice generated afterward calculates the correct tax split, includes the mandatory fields, and exports as a clean PDF.

For a quick one-off invoice without setting up a full account, DeskPanda also offers a [free GST invoice generator](/free-tools/gst-invoice-generator) — no signup required, generates a compliant PDF in under a minute.