How to Create a GST-Compliant Invoice in India (Step-by-Step)

A GST-compliant tax invoice isn't just "an invoice with a tax amount on it" — GST law specifies a fairly exact list of fields that need to be present for it to count as a valid tax invoice, the kind your customer can actually use to claim input tax credit. Here's the full list, in the order you'd naturally fill them in, plus the mistakes that are easy to make even when you know the rules.

Step 1 — Supplier details

• Your legal/trade name
• Your registered address
• Your GSTIN — this is non-negotiable; an invoice without it isn't a valid tax invoice

Step 2 — Invoice number and date

The invoice number must be a consecutive serial number, unique for the financial year, using only letters, numbers, hyphens, and slashes, up to 16 characters. This is the exact requirement set out in GST Rule 46(b) — worth reading in full if you're setting up a numbering scheme from scratch, since gaps or duplicates (even accidental ones) make the invoice non-compliant.

Step 3 — Customer details

• Customer's name and address
• Customer's GSTIN, if they're registered — this single field is what determines whether you charge CGST+SGST or IGST, so double-check it rather than assuming from the billing address

Step 4 — HSN or SAC code

Every line item needs an HSN code (Harmonized System of Nomenclature, for goods) or SAC code (Services Accounting Code, for services). The number of digits required depends on your turnover — smaller businesses can use fewer digits than larger ones. Getting this wrong doesn't usually change the tax amount, but it's still a compliance field auditors do check, so it's worth confirming the correct code once per product/service and reusing it consistently, rather than guessing per invoice.

Step 5 — Description, quantity, and rate

A clear description of each good or service, the quantity (for goods) or unit of measure, and the rate per unit — these should multiply out cleanly to the line's taxable value. Vague line items ("Services rendered — ₹50,000") are technically allowed but make an invoice look sloppy and are more likely to draw questions.

Step 6 — Taxable value and tax split

For each line: the taxable value (before tax), the applicable GST rate, and the tax amount split correctly into CGST + SGST (same state) or IGST (different states) — see our full breakdown of how that split is decided. This is the field most likely to be silently wrong, because an invoice with the wrong split can still add up to the correct total.

Step 7 — Place of supply

The state where the supply is deemed to take place — this should be explicitly stated, especially for inter-state supplies, since it's the field that justifies the IGST vs CGST+SGST decision above.

Step 8 — Total and amount in words

The final payable amount, ideally also written out in words (e.g. "Rupees Twenty-Nine Thousand Five Hundred Only") — a long-standing invoicing convention that makes tampering or misreading harder, and is expected on most professionally-formatted tax invoices.

Step 9 — Signature

A tax invoice should carry the supplier's signature or digital signature. For a digitally-generated PDF invoice, a scanned or uploaded signature image reproduced on the document satisfies this in practice.

The mistakes that slip through even when you know all nine steps

• Reusing an invoice number after voiding or deleting a previous invoice, instead of leaving a documented gap or continuing the sequence.
• Guessing the tax split from the customer's mailing address instead of their GSTIN's registered state.
• Copy-pasting an old invoice as a template and forgetting to update the HSN/SAC code for a genuinely different line item.
• Two people issuing invoices from the same numbering series without any coordination, which is how accidental duplicate numbers happen.

Every one of these is a "someone has to remember" problem — which is exactly the class of mistake that goes away once the numbering, tax split, and required fields are generated automatically from the party and invoice data, rather than typed by hand each time.