Tax invoice under GST: mandatory details and timing
A tax invoice is the document a GST-registered supplier issues for taxable supplies under section 31. It must carry GSTIN, HSN or SAC and tax details.
Short answer
A tax invoice is the document a registered supplier issues under section 31 of the CGST Act, 2017 when making a taxable supply. It records the supply, the value and the GST charged, and it is the primary document the recipient needs to claim input tax credit. Rule 46 of the CGST Rules lists the details it must contain.
- Governed by
- Section 31 and rule 46
- Serial number
- Consecutive, up to 16 characters, unique for the year
- Services timing
- Within 30 days of supply (45 days for banks and NBFCs)
- Exempt or composition
- Bill of supply instead
Mandatory contents
Rule 46 requires a tax invoice to include specific details. The most important ones are listed here, and taxpayers covered by e-invoicing must also carry the IRN and QR code on each B2B invoice.
- Supplier's name, address and GSTIN
- Consecutive serial number and date
- Recipient's name, address and GSTIN if registered
- HSN or SAC code, as required by turnover
- Description, quantity and value of goods or services
- Tax rate and amount of CGST, SGST or IGST
- Place of supply, with state name for inter-state supplies
- Whether tax is payable under reverse charge
- Signature or digital signature of the supplier
When to issue the invoice
For goods, the invoice is issued before or at the time of removal for supply or delivery. For services, it is issued within 30 days of the supply, or 45 days for insurers, banks and financial institutions including NBFCs. For continuous supplies, invoices follow the payment or milestone schedule in the contract. Errors are corrected through credit or debit notes rather than altering the original invoice.
Why it matters for startups
Customers cannot claim credit without a proper invoice, and missing fields lead to disputes or delayed payment. Configure your billing system with correct GSTINs, place of supply, codes and serial numbering, and if you cross the e-invoicing threshold, integrate with the IRP so every B2B invoice carries a valid IRN.
Related services
Sources
Written by the Refogo Editorial Team from the official sources above and checked on 2026-10-31. Laws, rates and due dates change, and authorities often extend deadlines, so confirm your own case with a qualified professional. This is general information, not legal or tax advice. Read our editorial policy or report an error to support@refogo.com.
Common questions
Can I issue a tax invoice without GST registration?
No. Only registered persons can issue tax invoices and charge GST. Unregistered businesses issue ordinary bills without GST.
Is a digital signature required on GST invoices?
Rule 46 requires a signature or digital signature, but e-invoices validated by the IRP need not be separately signed.
What is a bill of supply?
A document issued instead of a tax invoice for exempt supplies or by composition taxpayers, without charging GST.