GST billing software should apply HSN/SAC codes and the correct CGST/SGST/IGST split automatically, generate a valid e-Invoice IRN where your turnover requires it, and keep working if your connection drops — free tiers vary a lot in whether GST-specific fields are actually included or paywalled.
"GST billing software" covers a huge range of tools, from a generic invoice template with a tax field bolted on to software that genuinely automates HSN/SAC codes and e-Invoice IRNs. Here's what actually separates the two, rather than a ranked list of names.
Does it apply HSN/SAC codes automatically?
Every GST invoice line needs an HSN (goods) or SAC (services) code, and the required digit-length depends on your turnover bracket. The useful version of this feature sets the code once per item and applies it to every future invoice automatically — not a free-text field you retype each time you bill.
Does it generate a valid e-Invoice IRN, if you need one?
Above the e-invoicing turnover threshold, a B2B invoice needs to be reported to the government's Invoice Registration Portal (IRP) and carry the IRN and QR code it returns. "e-Invoice ready" in a product description isn't the same as actually integrating with the IRP — check whether the software produces a real IRN, or just a field you'd fill in from somewhere else.
Does the free tier actually include GST fields?
A lot of "free GST billing software" turns out to be a free invoice template with the GST-specific fields — HSN/SAC, tax-rate splits, e-Invoice support — gated behind a paid plan. Before assuming a free tier covers you, check specifically whether it handles GST invoicing, not just invoicing in general.
Does it split CGST/SGST vs IGST correctly?
If the buyer is in the same state as your registered business, GST splits into CGST and SGST at half the rate each; a different state means IGST at the full rate instead. This needs to be determined per invoice from the buyer's location — a flat "GST rate" field that doesn't do this split is a compliance gap waiting to surface at reconciliation time.
Does it hold up with a patchy connection?
Plenty of billing software is cloud-only, which becomes a real problem the moment a shop counter's signal drops mid-sale. Offline-first software keeps billing working with no connection and syncs once you're back online — worth testing directly rather than assuming a mobile app implies offline support.
A short checklist
StashBill's GST/VAT compliance engine covers HSN/SAC automation, e-Invoice IRN generation, and offline reliability — see pricing to check what's included free.Frequently asked
Is free GST billing software actually usable for real invoicing?
It depends on the tool — check specifically whether HSN/SAC codes and tax-rate splits are included in the free tier, or whether the free tier is a generic invoice template with GST fields paywalled.
Do small businesses need e-Invoicing?
Only if turnover is above the threshold the GST Council sets for mandatory e-invoicing; below that, an IRN isn't required, though HSN/SAC codes on your invoices still are.
What's the difference between GST billing software and a general invoicing app?
GST billing software specifically automates HSN/SAC codes, the CGST/SGST/IGST split, and e-Invoice IRN generation; a general invoicing app may only offer a flat tax-rate field that doesn't match what GST filing actually requires.