I've seen small business owners design beautiful invoices — logo, colours, nice layout — that were still technically non-compliant because of one missing field. Nobody notices until a customer's accounts team sends it back asking for a "proper GST invoice," or worse, it surfaces during an audit. The format can be whatever you want. The fields can't be optional.
Under Rule 46 of the CGST Rules, here's what a valid tax invoice actually needs.
The mandatory fields
Supplier details — your legal business name, address, and GSTIN. This has to match your actual GST registration exactly, not a shortened or informal version of your business name.
Invoice number and date — a unique, sequential invoice number (up to 16 characters) for the financial year, and the date of issue. You cannot skip numbers or reuse them. If invoice #104 is followed by #106, that gap will raise questions during reconciliation.
Recipient details — the buyer's name and address, and their GSTIN if they're a registered business (mandatory for B2B invoices; for B2C sales below a threshold, less detail is required).
Place of supply — required especially for inter-state transactions, since it determines whether CGST+SGST or IGST applies.
HSN or SAC code — the classification code for the goods (HSN) or service (SAC) being billed. This determines the correct GST rate and is checked against what you've declared in your returns.
Description, quantity, and taxable value — what was sold, how many units (or the service rendered), and the value before tax.
GST rate and tax amount — the applicable rate (0%, 5%, 18%, or 40% under the current structure — see below) and the computed tax, split as CGST + SGST for intra-state sales or shown as IGST for inter-state sales.
Total invoice value — the final amount payable, inclusive of tax.
Signature — of the supplier or an authorised representative (a digital signature satisfies this for electronic invoices).
A few fields are conditional rather than universal — delivery address (only if different from the place of supply), export/SEZ-specific declarations, and reverse-charge markers apply only when relevant to that particular transaction.
A quick note on GST rates
Since the GST 2.0 reform took effect on 22 September 2025, the old 12% and 28% slabs no longer exist. The current structure is 0% (exempt essentials), 5% (mass-consumption goods), 18% (the standard rate for most goods and services), and 40% (sin and luxury goods only — tobacco, pan masala, luxury vehicles). Make sure whatever rate you're billing at reflects this current structure — invoices still floating around with 12% or 28% on them are using an outdated rate.
The e-invoicing requirement — who it applies to
If your business crosses a certain aggregate annual turnover, you're required to generate invoices through the government's e-invoicing system, which assigns an IRN (Invoice Reference Number) and a QR code to each invoice before it's considered valid for GST purposes. This isn't optional once you're above the threshold — invoices without the IRN/QR code aren't treated as valid tax invoices for that category of business.
As of now, this threshold sits at businesses with aggregate annual turnover above ₹5 crore in any financial year since GST's rollout in 2017-18 — and once you've crossed it even once, the requirement sticks even if your turnover later drops below that figure. Thresholds have moved several times since e-invoicing was introduced, so if you're near the line, it's worth double-checking the current figure on the GST portal rather than assuming last year's rule still applies.
Why getting this right matters beyond just "following the rules"
An invoice missing mandatory fields isn't just a compliance technicality — it can mean your customer can't claim Input Tax Credit on it, which is a real cost to them and a real reason for them to push back on paying you, or to ask you to reissue it. A properly compliant invoice avoids that friction entirely.
Generate GST-compliant invoices with all the mandatory fields built in — including automatic CGST/SGST/IGST splitting and HSN/SAC lookup — using our GST Invoice Generator.