nodejs

UBL for Node.js: InvoiceXML API Examples

Node.js code samples for creating, validating, and parsing UBL electronic invoices using the InvoiceXML API. Compatible with Node.js 18 and later (native fetch and FormData). Runs in Express, NestJS, Fastify, Koa, Hapi, Next.js API routes, AWS Lambda, Cloudflare Workers, Vercel Functions, or plain scripts. Zero npm dependencies.

For background on UBL itself (what it is, the profiles, where it is used), see the main repository README.

Get your API key

Every example in this folder calls the InvoiceXML REST API. Sign up and generate a free API key here:

→ https://www.invoicexml.com/account/authentication

Pass it as a Bearer token on every request:

Authorization: Bearer YOUR_API_KEY

Important: set apiKey in the examples to the raw key only, without the Bearer prefix. If your account page shows the full header value (e.g. Bearer ixml_a1b2c3...), copy only the part after Bearer . The code adds the prefix itself when building the Authorization header.

Requirements

• Node.js 18.0 or later (current LTS recommended: Node 20 or 22)
• No npm packages, no package.json needed

The examples use Node's built-in global fetch, FormData, Blob, and Buffer. These have been stable in Node 18+. If you must support Node 16 or older, polyfill fetch with node-fetch and FormData with form-data.

Files in this folder

File	Operation	API endpoint
create.js	Build a UBL 2.1 XML invoice	POST /v1/create/ubl
validate.js	Validate a UBL file against the EN 16931 and Peppol rules	POST /v1/validate/ubl
extract-json.js	Parse a UBL XML into JSON	POST /v1/extract/json
ai-convert.js	(Experimental) Convert a plain PDF to UBL with AI	POST /v1/transform/to/ubl
render.js	Render UBL XML into a human-readable PDF	POST /v1/render/ubl/to/pdf

Each file is standalone and runnable with node create.js. Open the file, replace YOUR_API_KEY with your real key, and execute.

Note on the snippets below: they are excerpts from those files and assume apiKey (and fs) are already defined. They also use await at the top level, which is not valid in a plain CommonJS script; the full files wrap the calls in an async IIFE. When in doubt, copy the complete file.

---

Create a UBL invoice in Node.js

const payload = {
    invoice: {
        invoiceNumber: 'UBL-2026-001',
        issueDate:     '2026-05-18',
        currency:      'EUR',
        buyerReference: 'PO-2026-5571',
        seller: {
            name:              'Acme GmbH',
            vatIdentifier:     'DE123456789',
            legalRegistration: { identifier: 'HRB 12345' },
            postalAddress: { line1: 'Hauptstraße 12', city: 'Berlin', postCode: '10115', country: 'DE' },
            electronicAddress: { identifier: 'DE123456789', schemeId: '9930' },
        },
        buyer: {
            name: 'Globex SAS',
            postalAddress: { line1: '15 rue de Rivoli', city: 'Paris', postCode: '75001', country: 'FR' },
            electronicAddress: { identifier: 'FR40303265045', schemeId: '9957' },
        },
        paymentDetails: { paymentAccountIdentifier: 'DE89370400440532013000' },
        lines: [{
            quantity:       10,
            priceDetails:   { netPrice: 150.00 },
            vatInformation: { rate: 19.00 },
            item:           { name: 'Senior consulting' },
        }],
    },
    options: { profile: 'peppol-bis-3' },
};

const response = await fetch('https://api.invoicexml.com/v1/create/ubl', {
    method: 'POST',
    headers: {
        'Content-Type': 'application/json',
        Authorization: 'Bearer ' + apiKey,
    },
    body: JSON.stringify(payload),
});

fs.writeFileSync('invoice-ubl.xml', await response.text());

options.profile decides both the CustomizationID stamped into the document and the rules it is validated against. Peppol BIS Billing 3.0 is the default and needs an electronicAddress on both parties plus a buyerReference; for invoices that never touch the Peppol network, set the profile to en16931 and those become optional.

The response is the UBL 2.1 XML document, validated against the profile's rules before delivery.

Full example: create.js | API reference

---

Validate a UBL file in Node.js

const fs = require('fs');

const form = new FormData();
form.append('file', new Blob([fs.readFileSync('invoice.xml')], { type: 'application/xml' }), 'invoice.xml');

const response = await fetch('https://api.invoicexml.com/v1/validate/ubl', {
    method: 'POST',
    headers: { Authorization: 'Bearer ' + apiKey },
    body: form,
});

console.log(await response.text());

Returns a JSON validation report listing any rule failures (EN 16931 BR-* and BR-CO-, plus the CIUS rules, e.g. PEPPOL-EN16931- for Peppol BIS).

Full example: validate.js | API reference

---

Extract UBL data as JSON in Node.js

Useful for feeding UBL invoices into Express controllers, message queues, or any pipeline that prefers JSON over XML.

const fs = require('fs');

const form = new FormData();
form.append('file', new Blob([fs.readFileSync('invoice.xml')], { type: 'application/xml' }), 'invoice.xml');

const response = await fetch('https://api.invoicexml.com/v1/extract/json', {
    method: 'POST',
    headers: { Authorization: 'Bearer ' + apiKey },
    body: form,
});

const { invoice } = await response.json();
// The invoice document sits under the "invoice" key of the response.
console.log(invoice.seller.name, invoice.totals.grandTotalAmount);

Full example: extract-json.js | API reference | Sample response

---

(Experimental) Convert a plain PDF to UBL with AI

Experimental feature. Human verification required before any production use.

Real-world PDF invoices are often messy: scanned at low quality, irregularly formatted, multi-page, or missing fields that EN 16931 requires. AI extraction can make subtle mistakes that automated validators may not catch: wrong tax category codes, transposed amounts, missing seller VAT identifiers, incorrect currency formatting.

Always review the output before sending it to a customer or tax authority. See the AI conversion notes in the main README.

The endpoint takes the PDF alone; no extra parameters are needed.

Full example: ai-convert.js | API reference

---

Render UBL as a readable PDF in Node.js

UBL has no visual layer: the XML is the invoice, which is fine for machines and useless for the person in accounts payable who wants to read it. This endpoint renders the XML into a formatted PDF preview, auto-detecting whether the file is CII or UBL syntax. The PDF is for reading only; the XML file remains the authoritative invoice for compliance and tax purposes.

const fs = require('fs');

const form = new FormData();
form.append('file', new Blob([fs.readFileSync('invoice.xml')], { type: 'application/xml' }), 'invoice.xml');
form.append('language', 'de');   // en, de, or fr

const response = await fetch('https://api.invoicexml.com/v1/render/ubl/to/pdf', {
    method: 'POST',
    headers: { Authorization: 'Bearer ' + apiKey },
    body: form,
});

fs.writeFileSync('invoice-preview.pdf', Buffer.from(await response.arrayBuffer()));

Full example: render.js | API reference

---

Framework integration

Express

Return a UBL invoice from a route handler:

const express = require('express');
const app = express();

app.get('/invoices/:id/ubl', async (req, res) => {
    const pdf = await createUBL(req.params.id);
    res.setHeader('Content-Type', 'application/pdf');
    res.setHeader('Content-Disposition', `attachment; filename="invoice-${req.params.id}.pdf"`);
    res.send(pdf);
});

Store the API key in process.env.INVOICEXML_API_KEY and read it from dotenv or your platform's secret manager.

NestJS

@Controller('invoices')
export class InvoiceController {
    @Get(':id/ubl')
    @Header('Content-Type', 'application/pdf')
    async download(@Param('id') id: string, @Res() res: Response) {
        const pdf = await this.ublService.create(id);
        res.setHeader('Content-Disposition', `attachment; filename="invoice-${id}.pdf"`);
        res.send(pdf);
    }
}

Next.js App Router

// app/api/invoices/[id]/ubl/route.ts
export async function GET(req: Request, { params }: { params: { id: string } }) {
    const pdf = await createUBL(params.id);
    return new Response(pdf, {
        headers: {
            'Content-Type': 'application/pdf',
            'Content-Disposition': `attachment; filename="invoice-${params.id}.pdf"`,
        },
    });
}

Cloudflare Workers and Vercel Edge

The examples run on Workers and Edge runtimes unchanged because fetch and FormData are part of the runtime. Replace fs.readFileSync with an await request.arrayBuffer() from the inbound request and the same pattern works in serverless environments.

AWS Lambda (Node.js 18+)

Lambda's Node.js 18+ runtime provides native fetch and FormData, so the examples run as-is.

---

Common issues

• fetch is not defined: you are running Node 16 or older. Upgrade to Node 18+ (current LTS), or polyfill with npm install node-fetch form-data and import accordingly.
• HTTP 401 Unauthorized: API key missing or invalid. Generate one at invoicexml.com/account/authentication and confirm you are sending Authorization: Bearer YOUR_API_KEY. A frequent cause: setting apiKey to the whole Bearer xxx value, which sends Bearer Bearer xxx. Set the raw key only.
• HTTP 400 Bad Request on Create: a required field is missing or malformed. Frequent causes: IssueDate not in ISO format (YYYY-MM-DD), Currency not in ISO 4217 (EUR, USD), country codes not in ISO 3166-1 alpha-2 (DE, FR).
• ESM vs CommonJS: the examples use CommonJS (require). For ESM (.mjs extension or "type": "module" in package.json), swap require('fs') for import fs from 'node:fs' and you can use top-level await without the IIFE wrapper.
• Relative file paths: fs.readFileSync('invoice.xml') resolves from the current working directory, not the script file. Use __dirname (CommonJS) or import.meta.dirname (ESM, Node 20.11+) for absolute paths.
• PEPPOL-EN16931- failures on Validate*: a Peppol-specific requirement is missing. The most common are a missing electronic address on the seller or buyer, and a missing buyerReference (Peppol requires a buyer reference or a purchase order reference).

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Resources

• Get an InvoiceXML API key
• Create UBL API reference
• Validate UBL API reference
• Extract JSON API reference
• Extract XML API reference
• Transform to UBL API reference
• Node.js fetch API documentation
• Main repository README