E-invoicing under GST does not mean emailing a PDF. It means reporting each B2B invoice to a government Invoice Registration Portal (IRP), which checks it, signs it and returns an Invoice Reference Number (IRN) and a signed QR code. Only an invoice with a valid IRN counts as a tax invoice for those transactions, and the buyer's input tax credit depends on it.
This guide explains who needs e-invoicing, how the flow works, how e-way bills fit in, and how to stop doing it by hand. If you want to see the automated version first, try the e-invoice and e-way bill demo.
Rules and thresholds change by notification. Treat this as a guide to how the system works, and confirm the current limits for your business with your CA.
Who has to generate e-invoices
E-invoicing applies to registered businesses whose aggregate annual turnover crossed the notified threshold in any financial year since 2017-18. The threshold has come down in stages; at the time of writing it is ₹5 crore. Once you cross it, e-invoicing applies from then on, even if turnover falls later.
It covers:
- B2B invoices — sales to other GST-registered businesses
- Exports, and supplies to SEZ units
- Credit and debit notes against those invoices
Some sectors are exempt — for example banks, insurance companies and NBFCs, goods transport agencies, passenger transport and SEZ units themselves. B2C invoices do not need an IRN, although large businesses have separate dynamic-QR rules for them.
How the flow works
- Your billing creates the invoice in the standard e-invoice schema: seller, buyer GSTIN, items with HSN codes, values and taxes.
- The invoice data is sent to an IRP — directly by API, through a GST Suvidha Provider (GSP), or by uploading a JSON file on the portal.
- The IRP validates it: GSTINs active, totals consistent, no duplicate invoice number for the year.
- The IRP returns the IRN, an acknowledgement number and date, and a signed QR code.
- You print the QR code on the invoice and share it with the buyer. The details also flow to the GST system, which pre-fills your GSTR-1.
Done by hand, steps 2 to 5 mean exporting a file, logging in, uploading, downloading the signed response and copying the IRN and QR back into your invoice — for every invoice. Done through an API, it happens when you save the invoice.
Time limits that matter
- Reporting window. Larger taxpayers (at the time of writing, those with annual turnover of ₹10 crore or more) cannot report an invoice to the IRP more than 30 days after its date. A late invoice can't get an IRN — which makes it a problem for your buyer's credit.
- Cancellation window. An IRN can be cancelled only within 24 hours of generation, and only as a whole. After that, corrections go through a credit or debit note.
Both are easy to miss with manual uploads and impossible to miss when the software generates the IRN as soon as the invoice is saved.
Where the e-way bill comes in
Goods worth more than ₹50,000 moving by road usually need an e-way bill (some states set different limits for movement within the state). It has two parts:
- Part A — invoice, consignor, consignee, goods and value
- Part B — the vehicle number or transport document
Validity depends on distance: for normal cargo, one day for every 200 km or part of it. It runs till midnight of the last day.
Because Part A is the same data as the e-invoice, an e-invoice system can generate the e-way bill along with the IRN, or from it in one step — the distance is worked out from the two pincodes and only the vehicle number is added. No retyping on a second portal.
Common reasons invoices get rejected
- Inactive or cancelled buyer GSTIN — check it when the customer is created, not at the gate.
- Duplicate invoice number in the same financial year, often after a manual retry.
- Wrong HSN codes or tax rates for an item.
- Totals that don't add up because of rounding at line level.
- Wrong state codes — for example, IGST charged on an intra-state supply.
Good software catches these before sending, explains the rejection when one happens, and keeps a log so nobody has to remember what went wrong last Tuesday.
Automating it: three ways
| Approach | Good for | Watch out for |
|---|---|---|
| Manual JSON upload on the portal | A handful of invoices a month | Slow, error-prone, easy to miss the windows |
| Your accounting software's built-in e-invoicing | Standard billing in one system | Limited if orders come from a website, ERP or several systems |
| API integration in your own billing or ERP | Many invoices, several sources, dispatch from a godown | Needs a GSP account and a careful build |
For most businesses billing dozens of invoices a day, the third option pays for itself in staff time and in trucks that leave the gate on time.
What to ask before you build or buy
- Does it generate the IRN when the invoice is saved, without a separate step?
- Can it create the e-way bill from the same invoice, and update Part B from the gate?
- What happens when the IRP is down? (Invoices should queue and retry automatically.)
- Is every IRN, cancellation and rejection logged with the user and time?
- Does it handle credit notes, multiple GSTINs and branch transfers the way your business does?
The short version
E-invoicing is a reporting step that sits between your invoice and your buyer's input tax credit. Done by hand, it is slow and easy to get wrong; done from your billing, it takes one click — and the e-way bill comes with it.
See the e-invoice and e-way bill demo, the GST billing software demo, or talk to us about your billing.