ZATCA E-Invoicing SDK

TypeScript SDK for Saudi Arabia's ZATCA Phase 2 e-invoicing (Fatoora). Runs on Bun with zero OpenSSL/CLI dependencies — all cryptography (secp256k1 keys, CSR, XAdES signatures) is pure JS.

Every signed invoice is verified end-to-end before it leaves the SDK: the invoice hash is recomputed from the final XML bytes exactly the way ZATCA's validator recomputes it, and the ECDSA signature is verified against the signing key. Output passes the official ZATCA SDK validator (XSD, EN 16931, KSA schematron, QR, signature, PIH) and the live sandbox compliance/reporting/clearance APIs.

Environments

Env	Base URL	CSR template	OTP
sandbox	…/developer-portal	TSTZATCA-Code-Signing	any value
simulation	…/simulation	PREZATCA-Code-Signing	from Fatoora portal
production	…/core	ZATCA-Code-Signing	from Fatoora portal

Sandbox quirk: the developer portal issues a canned certificate that never matches your CSR key. The SDK detects this and relaxes its cert/key self-check on sandbox only; on simulation/production a mismatch is a hard error.

Quick start

import { ZATCAClient, type EGSUnitInfo, type Invoice } from "zatca-sdk";

const egsUnit: EGSUnitInfo = {
    uuid: crypto.randomUUID(),
    branchName: "Riyadh Branch",
    branchIndustry: "Supply activities",
    location: "RRRD2929",                       // national short address
    commonName: "TST-886431145-399999999900003",
    organizationName: "My Company LTD",
    countryCode: "SA",
    vatNumber: "399999999900003",               // 15 digits, starts/ends with 3
    invoiceType: "1100",                        // standard + simplified
};

const client = new ZATCAClient({ env: "sandbox", egsUnit, solutionName: "MyERP" });

// 1. Onboard once (OTP from the Fatoora portal; any value on sandbox)
await client.onboard("123456");
persist(client.getState()); // contains private key + secrets — encrypt at rest

// 2. Sign + submit (simplified → reporting, standard → clearance)
const result = await client.submitInvoice(invoice);
if (result.success && result.data.accepted) {
    console.log("hash:", result.data.signedInvoice.invoiceHash);
    console.log("QR:", result.data.signedInvoice.qrTlvBase64);
}
persist(client.getState()); // ICV + PIH chain advanced — always persist

Restore across restarts with new ZATCAClient({ ..., state: persistedState }). The ICV counter and PIH chain live in that state — losing it breaks the invoice chain.

Onboarding on simulation/production

Those environments require compliance checks between the compliance CSID and production CSID:

await client.startOnboarding(otp);                    // keys + CSR + compliance CSID
await client.checkInvoiceCompliance(sampleInvoice);   // once per declared invoice type
await client.finishOnboarding();                      // production CSID

Low-level API

Every step is usable standalone:

import {
    generateKeyPair, generateCSR,             // secp256k1 + ZATCA CSR (pure JS)
    signInvoice, computeInvoiceHash,          // signing pipeline
    parseCertificate, validateCertificate,    // X.509 DER parsing
    generateTLVString, decodeTLVString,       // Phase 2 QR TLV
    buildInvoiceXml,                          // UBL 2.1 document
} from "zatca-sdk";

signInvoice(invoice, { credentials }) returns the signed XML, invoice hash, base64 payload, and QR — with post-signing hash/signature self-checks already done.

Invoice model

Invoice covers: standard (invoiceSubType 01…) and simplified (02…) invoices, credit notes (381) and debit notes (383, both need billingReference + creditDebitReason), line discounts, document-level allowances, zero-rated/exempt lines (exemptionReasonCode), non-SAR document currencies (taxExchangeRate, taxTotalInSAR), and prepaid/rounding amounts.

validateInvoice(invoice) runs structural + arithmetic checks (BR-KSA seller address rules, BR-CO totals consistency) and is called automatically by signInvoice.

Verification

bun test                        # unit + golden-fixture tests (offline)
bun run test:sandbox            # live sandbox: onboarding → compliance → reporting/clearance
bun run validate:fatoora        # official ZATCA validator (needs Java 11, see below)

The golden fixtures are the official ZATCA SDK's test certificate/key and its own signed output — the tests assert byte-exact agreement on certificate digests, issuer formatting, QR TLV bytes, and signature verification.

validate:fatoora runs the official Java validator vendored in resources/. It needs Java 11 (17+ removed secp256k1 from the JVM); set JAVA_HOME_11 if java isn't v11.

Design notes (read before touching signing)

• Hash-consistency by construction. The builder emits the complete document — including the QR AdditionalDocumentReference (placeholder) and cac:Signature scaffolding — before hashing. The hash is computed by stripping UBLExtensions/Signature/QR and canonicalizing, which is exactly what ZATCA's validator does to the submitted bytes. UBLExtensions is inserted byte-adjacent after <Invoice …> so stripping it restores the hashed byte stream.
• ZATCA's non-standard XAdES quirks (all deliberate, all validator-verified): the ECDSA signature is over the invoice-hash bytes (not SignedInfo); the certificate digest is SHA-256 of the base64 DER text, hex-encoded then base64; the SignedProperties digest is computed from a byte-exact template with 36-space indentation.
• QR TLV uses single-byte lengths (max 255 bytes per tag). Tags 6–7 store base64 strings; tags 8–9 store raw bytes (SPKI DER, cert signature). The timestamp is the literal issueDateTissueTime — never routed through Date.

Requirements

• Bun ≥ 1.0 (Node ≥ 18 works too — no Bun-specific APIs in src/)
• No OpenSSL, no Java at runtime (Java 11 only for the optional official-validator script)