GST invoicing looks simple on the surface: apply 18%, print the tax on the invoice, done. In practice, building GST-compliant invoicing into a web application requires handling a set of rules that most developers only discover after a client gets a notice.

CGST/SGST vs IGST — and why it matters for your database

Whether a transaction is intra-state or inter-state determines whether you apply CGST+SGST or IGST. This is not a display preference — it changes the tax columns on the invoice and the data that goes into GST returns. Your schema needs to handle both cases, not just calculate a total tax amount.

HSN codes and their validation

Every line item on a B2B GST invoice requires an HSN code. The digit length required depends on the annual turnover of the supplier. This is a data integrity problem, not a formatting one.

E-invoicing for registered businesses

Businesses above the e-invoicing threshold must generate an IRN (Invoice Reference Number) from the IRP before the invoice is considered valid. This is an API integration, not a document format. If your web app is generating invoices without IRN for clients above the threshold, the invoices are non-compliant.

At Magnustic, we have built GST-compliant invoicing into Qiyadah ERP from the ground up — handling CGST/SGST/IGST split, HSN validation, and e-invoicing API integration for clients who need it.

✦ Explore The Qiyadah Enterprise Ecosystem

Powering High-Growth Enterprises with Qiyadah ERP & Qiyadah eShip

Whether you need multi-warehouse inventory, double-entry GST/ZATCA accounting, or 100+ carrier AWB & COD logistics automation, explore our production-ready platforms:

Qiyadah ERP → General ledger, multi-branch stock, procurement, payroll & GST/ZATCA compliance. Qiyadah eShip ERP → Multi-carrier AWB generation, NDR automation, dynamic rate calculation & COD settlement.