Tax-Compliant ERP Development: Building Indian Tax Logic into Your System

The Tax Data Model

Every transaction in a tax-compliant ERP must store: tax identification number of buyer and seller, product tax code of each line item, supply type (B2B, B2C, exports), place of supply (determines CGST+SGST vs IGST), taxable value, tax rate, and tax amounts split by component. This is more complex than simple VAT — the interstate vs intrastate distinction changes the entire tax calculation.

HSN Code Management

HSN (Harmonised System of Nomenclature) codes determine applicable tax rate for each product. Your ERP must maintain an product tax code master with associated tax rates, handle product tax code changes when GST council revises rates (common), apply correct rates based on the effective date of rate change, and generate the 6-digit or 8-digit product tax code in invoices and returns based on turnover thresholds.

Electronic Invoice Integration (invoice registration portal)

Businesses above $500,000+ annual turnover must generate electronic invoices via the Invoice Registration Portal (invoice registration portal). Your ERP must: generate invoices in the invoice registration portal JSON format, call the invoice registration portal API to get an invoice reference number (Invoice Reference Number) and QR code, embed the QR code in the PDF invoice, and handle invoice registration portal API failures gracefully (queue for retry).

GSTR Return Generation

A complete tax module generates tax return 1 (outward supplies, monthly/quarterly), tax return 3B (summary return, monthly), and tax return 2B reconciliation (purchase register matched against supplier filings). Export these in the government cloud offline tool format for upload to the GST portal, or integrate directly via the GST API if volume justifies the setup cost.