Invoice Generator API: Getting Started Guide

The Invovate Invoice API lets you generate professional PDF invoices programmatically — from your backend, a serverless function, or a no-code automation tool. It accepts a JSON payload describing invoice details and returns either a PDF binary or a JSON confirmation.

This guide covers everything you need to go from zero to a generated invoice in under 10 minutes, including authentication, request format, and full code examples in cURL, JavaScript, and Python.

Prerequisites

• A free Invovate account (register here)
• An API key (generated in your dashboard under Settings → API)
• Basic familiarity with REST APIs and HTTP requests

Authentication

All API requests must include your API key as a Bearer token in the Authorization header:

Authorization: Bearer inv_your_api_key_here

API keys begin with inv_. Keep your key secret — treat it like a password. If a key is compromised, regenerate it immediately from your dashboard.

API Endpoint

Request Body

The API accepts Content-Type: application/json. Here is the full request schema:

{
  "output": "pdf",           // "pdf" or "json"
  "language": "en",          // en, nl, de, fr, es, it, pt, ar, ja, ru, hi
  "template": "classic",     // classic, modern, bold, minimal, navy
  "currency": "USD",         // ISO 4217 code
  "from": "Acme Corp\n123 Main St\nNew York, NY 10001",
  "to": "Client Name\nClient Address\[email protected]",
  "invoiceNumber": "INV-2026-001",
  "invoiceDate": "2026-04-01",
  "dueDate": "2026-05-01",
  "items": [
    {
      "description": "Web Development — April retainer",
      "quantity": 1,
      "rate": 2500.00,
      "tax": 0
    },
    {
      "description": "Domain renewal",
      "quantity": 2,
      "rate": 14.99,
      "tax": 20
    }
  ],
  "taxRate": 0,              // global tax % (overridden by per-item tax)
  "discount": 0,             // discount amount or %
  "discountType": "percent", // "percent" or "fixed"
  "amountPaid": 0,
  "notes": "Payment via bank transfer to: IBAN GB00 0000 0000 0000",
  "terms": "Net 30"
}

Example: cURL

curl -X POST https://invovate.com/api/generate-invoice \
  -H "Authorization: Bearer inv_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "output": "pdf",
    "language": "en",
    "template": "classic",
    "currency": "USD",
    "from": "Acme Corp\n123 Main St\nNew York NY 10001",
    "to": "Jane Smith\nAcme Client Co\[email protected]",
    "invoiceNumber": "INV-001",
    "invoiceDate": "2026-04-01",
    "dueDate": "2026-05-01",
    "items": [{"description":"Consulting","quantity":10,"rate":150,"tax":0}],
    "notes": "Thank you for your business."
  }' \
  --output invoice.pdf

If successful, the response body is the raw PDF binary. Use --output invoice.pdf to save it to disk.

Example: JavaScript (Node.js / fetch)

const fs = require('fs');

const payload = {
  output: 'pdf',
  language: 'en',
  template: 'modern',
  currency: 'EUR',
  from: 'Your Company GmbH\nMusterstraße 1\n10115 Berlin',
  to: 'Client Name\[email protected]',
  invoiceNumber: 'INV-2026-042',
  invoiceDate: '2026-04-01',
  dueDate: '2026-05-01',
  items: [
    { description: 'Software development', quantity: 40, rate: 95, tax: 19 }
  ],
  notes: 'Bitte überweisen Sie den Betrag innerhalb von 30 Tagen.'
};

const response = await fetch('https://invovate.com/api/generate-invoice', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer inv_your_api_key_here',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify(payload)
});

if (!response.ok) {
  const error = await response.json();
  throw new Error(error.error);
}

const pdfBuffer = Buffer.from(await response.arrayBuffer());
fs.writeFileSync('invoice.pdf', pdfBuffer);
console.log('Invoice saved to invoice.pdf');

Example: Python

import requests

payload = {
    "output": "pdf",
    "language": "nl",
    "template": "minimal",
    "currency": "EUR",
    "from": "Uw Bedrijf BV\nKeizersgracht 1\n1015 Amsterdam",
    "to": "Klant Naam\[email protected]",
    "invoiceNumber": "FACT-2026-001",
    "invoiceDate": "2026-04-01",
    "dueDate": "2026-05-01",
    "items": [
        {"description": "Webdesign", "quantity": 1, "rate": 1200, "tax": 21}
    ],
    "notes": "Betaling binnen 30 dagen via bankoverschrijving."
}

response = requests.post(
    "https://invovate.com/api/generate-invoice",
    headers={
        "Authorization": "Bearer inv_your_api_key_here",
        "Content-Type": "application/json"
    },
    json=payload
)

response.raise_for_status()

with open("factuur.pdf", "wb") as f:
    f.write(response.content)

print("Factuur opgeslagen als factuur.pdf")

Template Options

Supported Languages

The language parameter affects invoice labels (e.g. "Invoice" vs "Facture" vs "Rechnung"), date formats, number formats, and text direction. Arabic (ar) generates a fully right-to-left PDF. Japanese (ja) uses phonetic fallback characters for the current version.

Error Handling

On error, the API returns a JSON object with an error field and an appropriate HTTP status code:

// 401 Unauthorized
{ "error": "Invalid or missing API key" }

// 429 Too Many Requests
{ "error": "Rate limit exceeded", "reset": 1743542400 }

// 400 Bad Request
{ "error": "items is required and must be a non-empty array" }

Always check response.ok (or status codes) before attempting to read a PDF response. A 4xx/5xx response will contain JSON, not binary PDF data.

Generating JSON Instead of PDF

Set "output": "json" to receive a structured JSON response containing the calculated invoice totals instead of a binary PDF. This is useful for previewing invoices or building custom PDF renderers on your end.

Further Reading

• Full API Reference Documentation
• How to Create a Professional Invoice
• VAT Rates by Country 2026