What makes an invoice GST-compliant?
A GST invoice in India must contain specific mandatory fields. Missing any of them makes the invoice invalid for input tax credit purposes — which creates problems both for you and for your customer. The mandatory fields are:
- Name, address and GSTIN of the supplier
- Consecutive invoice serial number (unique per financial year)
- Date of issue
- Name, address and GSTIN (or UIN) of the recipient for registered buyers
- HSN or SAC code for each line item
- Description of goods or services
- Quantity and unit of measurement (for goods)
- Total value of supply
- Taxable value after discounts
- Rate and amount of CGST, SGST, IGST or UTGST as applicable
- Place of supply (state code) for inter-state supplies
- Whether the supply is intra-state or inter-state
- Signature or digital signature of the supplier
CGST vs SGST vs IGST — when does each apply?
The applicable tax type depends on whether the supply is within the same state (intra-state) or crosses state lines (inter-state):
- Intra-state supply: CGST (Central GST) + SGST (State GST), each at half the applicable rate.
- Inter-state supply: IGST (Integrated GST) at the full applicable rate.
- Union territories: CGST + UTGST instead of CGST + SGST.
Getting this wrong — for example raising an IGST invoice for what should be an intra-state supply — creates a GST liability mismatch that requires amendment invoices and credit notes to resolve.
E-invoicing requirements
E-invoicing (electronic invoice registration on the GST portal's Invoice Registration Portal, or IRP) is mandatory in India for businesses above certain aggregate turnover thresholds. Once registered on the IRP, the invoice receives an Invoice Reference Number (IRN) and a QR code that must appear on the physical or digital document. The threshold has been progressively lowered over time — check the GST portal for the current applicable limit.
Credit notes and debit notes
If an invoice needs to be corrected after issue:
- Issue a credit note if the value is being reduced (e.g. a return or a price reduction).
- Issue a debit note if the value is being increased (e.g. additional goods supplied or an undercharge discovered).
Credit and debit notes must reference the original invoice number and date.
How LeafyOps Accounts handles GST
LeafyOps Accounts generates GST-compliant invoices automatically. You configure your GSTIN, HSN/SAC codes and applicable rates once. The system then calculates CGST/SGST vs IGST based on the customer's state, applies the correct rates to each line item, and produces an invoice that meets the mandatory field requirements. Credit notes and debit notes are linked back to the original invoice. For businesses subject to e-invoicing, the IRN integration is handled natively — the invoice is registered with the IRP at the point of issue and the QR code is appended automatically.