GST E-Invoicing and E-Way Bill: What Software Must Handle
Software that handles GST e-invoicing must send each invoice to the Invoice Registration Portal (IRP), store the IRN, signed QR code and acknowledgement it returns, and then print or share only that registered invoice. For goods, it must also create an e-way bill when a consignment is worth more than ₹50,000, ideally from the same invoice data.
This guide lists what your billing, ERP or custom software has to do for both, the failure cases most vendors skip, and how to check a system before you buy or build one.
Key takeaways
- E-invoicing applies to businesses with aggregate turnover above ₹5 crore, under Notification 10/2023, in force since 1 August 2023 (Busy).
- At ₹10 crore and above, invoices must also be reported to the IRP within 30 days of the invoice date, for invoices dated on or after 1 April 2025 (The Tax Corp).
- An invoice that needs an IRN and lacks one is not a valid invoice, and the buyer cannot claim input tax credit on it (TaxGuru).
- An e-way bill is needed for goods worth more than ₹50,000 under Rule 138, and its validity is one day per 200 km (Masters India, Busy).
Who has to use e-invoicing, and what is the 30-day rule?
E-invoicing is mandatory for registered businesses whose aggregate turnover is above ₹5 crore. A business between ₹5 and ₹10 crore must get an IRN for every B2B invoice but is not subject to the 30-day reporting limit.
From ₹10 crore, the IRP will reject an invoice reported more than 30 days after its date. In software terms, that means an invoice you forgot to send last month may no longer be registrable at all. Your system needs a daily check for invoices that were created but never registered.
Two exclusions matter when you scope the build. Sales to unregistered consumers (B2C) do not need an IRN, though very large businesses must show a dynamic QR code on them (Sovos). Some classes of taxpayer are also exempt, so keep the rule configurable instead of hard-coding it.
Thresholds and dates have moved before. Confirm the current notification with your tax adviser before you fix them in code.
What must e-invoicing software do?
E-invoicing software must build the invoice in the government's JSON schema, send it to the IRP, and keep what comes back. The IRP returns an Invoice Reference Number (IRN), an acknowledgement number and date, and a signed QR code.
The IRN is a 64-character hash made from the supplier's GSTIN, the financial year, the document type and the invoice number. Because of that, one invoice number can only ever produce one IRN.
Here is the minimum feature list we use when we review a system:
| Requirement | Why it matters |
|---|---|
| Schema validation before sending | The IRP rejects bad GSTINs, HSN codes and totals that do not add up. Catch them at entry |
| Stores IRN, ack number, ack date, signed QR | The printed invoice must carry the QR; these fields are your proof |
| Locks the invoice after registration | Editing a registered invoice breaks the match with the IRP copy |
| Credit and debit note support | Corrections after the cancellation window go through notes |
| Document type and series control | The IRN depends on invoice number, so duplicates must be impossible |
| Daily "not yet registered" report | Protects against the 30-day limit |
| Audit log of every API call | Lets you prove what was sent, when |
When is an e-way bill needed, and how does it link to e-invoicing?
An e-way bill is needed when a registered person moves goods worth more than ₹50,000, whether for a sale, a branch transfer or another reason. Rule 138 of the CGST Rules sets the limit, with a list of exempt goods in Rule 138(14) (Masters India). Interstate job work needs one whatever the value.
The e-way bill has two parts. Part A holds the consignment and parties, and Part B holds the vehicle. Validity is one day for every 200 km or part of it for ordinary cargo (Busy).
For a business that already registers e-invoices, the sensible design is one screen and one set of data. Invoice, IRN and e-way bill come from the same record, so the transporter's name, vehicle and distance are entered once. Check with your GST service provider how it supports creating the e-way bill from an IRN, because the mechanics depend on the API access you use.
Your software also needs to handle the awkward parts of an e-way bill: 1. Changing the vehicle in Part B when a truck breaks down. 2. Extending validity when a delivery is delayed. 3. Cancelling a bill when goods never left. 4. Warning when a vehicle number is missing on the day of dispatch.
What happens when something goes wrong? (The part vendors skip)
The failure cases decide whether a system is usable, because the IRP and the e-way bill portal both go down and both reject things. A system that only works on the happy path will block your dispatch dock on the day it matters.
Ask any vendor, or your own developer, how the system behaves in each case:
- The IRP is slow or down. Does the invoice queue and retry on its own, or does a clerk re-click? Does the dispatch team still see the invoice's status?
- The call times out but the invoice was registered. A blind retry can return a duplicate IRN error. The system should fetch the existing IRN by invoice details, not fail.
- An invoice is wrong. An IRN can be cancelled only within 24 hours, and not partially. After that, you issue a credit note and report it (Busy). A cancelled invoice number cannot be reused.
- An e-way bill is already live. Cancel or amend the e-way bill first, or you leave goods on the road against a cancelled invoice.
- A customer's GSTIN is no longer active. Validate the GSTIN before the invoice is issued.
Should you buy a tool or build into your own system?
If you only issue invoices, a standalone billing tool with e-invoicing built in is usually enough. If invoices come from your ERP, dispatch system or customer portal, build the integration into that system, because retyping data into a second tool is where mismatches start.
| Situation | Better route | Watch out for |
|---|---|---|
| Few invoices, simple billing | Packaged billing tool | Export limits, one more login |
| ERP already in use | ERP's e-invoice module or connector | Customised invoice formats that break the schema |
| Custom portal or bespoke software | API integration through a GST service provider | Retry logic, audit trail, who owns upgrades |
| Heavy dispatch with e-way bills | Integrated invoice + dispatch flow | Vehicle changes and extensions |
For cost, see our guides on custom software development cost in India and ERP implementation cost. Compliance rules also change, so plan for a yearly maintenance budget. A manufacturer should also read what an ERP for a Gujarat manufacturing SME should cover, since invoicing and dispatch sit in the same workflow.
What we've seen at DECK IT
At DECK IT in Ahmedabad, we build business software for Indian companies, and GST invoicing is in almost every scope. The most common surprise is not the API call. It is that the invoice number series, the dispatch step and the e-way bill were designed separately, so nothing agreed with anything else.
Our advice is to decide early who is allowed to edit an invoice and when it locks. If the lock point is vague, finance ends up fixing registered invoices by hand. We also keep the registration status visible on the dispatch screen so the warehouse never ships against an invoice that failed. If you are scoping this inside a wider build, our custom software and web development team can walk through it with you.
Frequently asked questions
Who must generate an e-invoice under GST?
Registered businesses with aggregate turnover above ₹5 crore must generate an e-invoice for B2B supplies, under Notification 10/2023. B2C sales do not need an IRN. Some taxpayer classes are exempt, so confirm yours.
What is the 30-day rule for e-invoices?
Taxpayers with turnover of ₹10 crore or more must report an invoice to the IRP within 30 days of its date, for invoices dated on or after 1 April 2025. A late invoice cannot get an IRN. Your software should flag unregistered invoices well before day 30.
Can an e-invoice be cancelled?
Yes, but only within 24 hours of IRN generation, and not partially. After that, you must issue a credit note and report it. The invoice number of a cancelled e-invoice cannot be reused.
When is an e-way bill required?
An e-way bill is required when the consignment value exceeds ₹50,000 under Rule 138, unless the goods are exempt. Interstate job work needs one irrespective of value. Some states set their own rules for movement within the state.
How long is an e-way bill valid?
Validity is one day for every 200 km or part of it for ordinary cargo, and one day per 20 km for over-dimensional cargo. Delays can usually be handled by extending the bill before it expires.
What happens if an invoice has no IRN?
An invoice that needs an IRN but lacks one is not a valid invoice, and the buyer cannot claim ITC on it. A penalty can also apply, reported at the higher of ₹10,000 or the tax involved (Tally).
Conclusion
Before you buy or build, test the failure cases: IRP downtime, duplicate IRN, cancellation with a live e-way bill, and the 30-day check. A system that passes those will cope with the ordinary days as well.
If you want a second opinion on a quote or a scope, we are happy to review it.