@zenuinebit/einvoice-irn

Builds the e-invoice JSON (IRP "INV-01" layout) for a GST invoice and computes its IRN. Includes a small SHA-256, so it runs in Node and the browser with no extra dependency. Builds on @zenuinebit/gst-report, @zenuinebit/address-india and @zenuinebit/invoice-number.

Check before you rely on it. Field names, codes and limits follow the e-invoice schema as commonly documented. The schema, the IRN rule and who must use e-invoicing change over time. Validate the JSON with the official tools or the IRP sandbox first. Only B2B supplies are built.

import { buildEinvoice, toEinvoiceJson, irnFor, computeIrn, cancelPayload } from "@zenuinebit/einvoice-irn";

const input = {
  invoice: {                                       // the same SaleInvoice used by gst-report (tax-exclusive prices)
    number: "INV/2025-26/0042",
    date: "2025-04-10",
    placeOfSupply: "Karnataka",
    buyer: { gstin: "29ABCPD1234E1ZA", name: "Bengaluru Traders" },
    lines: [{ description: "Tea 250g", hsn: "0902", quantity: 10, unitPrice: 10_000, taxRate: 5 }],
  },
  seller: { gstin: "27AAPFU0939F1ZV", name: "ZenuineBit Foods Pvt Ltd", address1: "1 Main Rd", place: "Pune", pincode: "411001" },
  buyer:  { gstin: "29ABCPD1234E1ZA", name: "Bengaluru Traders", address1: "5 MG Rd", place: "Bengaluru", pincode: "560001" },
  unitByHsn: { "0902": "KGS" },
};

const json = buildEinvoice(input);        // plain object: TranDtls, DocDtls, SellerDtls, BuyerDtls, ItemList, ValDtls
await fs.writeFile("einv.json", toEinvoiceJson(input));

irnFor(input);                            // 64-hex IRN of this invoice
computeIrn(sellerGstin, "INV", "INV/2025-26/0042", "2025-04-10");

cancelPayload(irn, "data-entry-mistake", "Wrong buyer");   // { Irn, CnlRsn: "2", CnlRem }

How it works

• IRN = SHA-256 of supplier GSTIN + financial year (2025-26) + document type (INV, CRN, DBN) + document number, as 64 lowercase hex characters. The portal computes it again when you register, so this lets you show or check it up front. It is tested against node:crypto.
• Amounts are in rupees, the date is dd/MM/yyyy, tax is CGST+SGST within a state and IGST between states (same maths as gst-report). An HSN starting with 99 is treated as a service.
• Credit notes keep positive amounts and use document type CRN.
• Throws a clear message for a bad GSTIN, PIN, HSN or SAC (4 to 8 digits), a document number the portal would refuse (1-16 characters, letters, digits, / and -, not starting with 0), tax-inclusive prices, or a missing buyer GSTIN.

Not included: calling the IRP (authentication, registration, QR code and signed invoice), B2C, exports and SEZ, dispatch and ship-to details, payment and reference details, cess, round-off, and the rules about who must issue e-invoices and by when.