Manual invoice creation is tedious and error-prone. Whether you bill clients monthly, process e-commerce orders, or manage subscription payments, automating your invoice pipeline saves time, reduces mistakes, and ensures consistent branding. In this tutorial, we will build a complete Node.js invoice automation system that integrates with Stripe, generates professional PDF invoices via TongoRender, and delivers them by email.
System Architecture
Our automated pipeline has four components:
- Data source — Stripe API for payment data (adaptable to any billing system)
- Template engine — HTML/CSS invoice template with dynamic data injection
- PDF renderer — TongoRender API to convert HTML to polished PDF
- Delivery — Nodemailer for email delivery with PDF attachment
Step 1: Fetch Payment Data from Stripe
const Stripe = require('stripe');
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);
async function getMonthlyInvoices(year, month) {
const startTimestamp = Math.floor(new Date(year, month - 1, 1).getTime() / 1000);
const endTimestamp = Math.floor(new Date(year, month, 0, 23, 59, 59).getTime() / 1000);
const charges = await stripe.charges.list({
created: { gte: startTimestamp, lte: endTimestamp },
limit: 100,
expand: ['data.customer'],
});
return charges.data
.filter(charge => charge.status === 'succeeded')
.map(charge => ({
id: charge.id,
amount: charge.amount / 100,
currency: charge.currency.toUpperCase(),
customerName: charge.customer?.name || 'Unknown',
customerEmail: charge.customer?.email,
description: charge.description || 'Service charge',
date: new Date(charge.created * 1000).toISOString().split('T')[0],
}));
}Step 2: Design the Invoice Template
Create a professional invoice template with proper print styling:
function invoiceHTML(invoice, companyInfo) {
return `
<!DOCTYPE html>
<html>
<head>
<style>
body { font-family: 'Segoe UI', sans-serif; color: #333; margin: 0; padding: 40px; }
.header { display: flex; justify-content: space-between; align-items: flex-start; margin-bottom: 40px; }
.company-name { font-size: 24px; font-weight: 700; color: #1a1a2e; }
.invoice-title { font-size: 32px; color: #e63946; text-align: right; }
.invoice-meta { text-align: right; color: #666; margin-top: 10px; }
.billing-section { display: grid; grid-template-columns: 1fr 1fr; gap: 40px; margin: 30px 0; }
.label { font-size: 12px; text-transform: uppercase; color: #999; letter-spacing: 1px; }
table { width: 100%; border-collapse: collapse; margin: 30px 0; }
th { background: #1a1a2e; color: white; padding: 12px 15px; text-align: left; font-size: 13px; }
td { padding: 12px 15px; border-bottom: 1px solid #eee; }
.total-row td { font-weight: 700; font-size: 16px; border-top: 2px solid #1a1a2e; }
.footer { margin-top: 40px; padding-top: 20px; border-top: 1px solid #eee; color: #999; font-size: 12px; }
</style>
</head>
<body>
<div class="header">
<div>
<div class="company-name">${companyInfo.name}</div>
<div>${companyInfo.address}</div>
<div>${companyInfo.taxId}</div>
</div>
<div>
<div class="invoice-title">INVOICE</div>
<div class="invoice-meta">
<div>Invoice #: ${invoice.number}</div>
<div>Date: ${invoice.date}</div>
<div>Due: ${invoice.dueDate}</div>
</div>
</div>
</div>
<div class="billing-section">
<div>
<div class="label">Bill To</div>
<div style="margin-top:8px">
<strong>${invoice.customerName}</strong><br>
${invoice.customerAddress || ''}
</div>
</div>
</div>
<table>
<thead>
<tr><th>Description</th><th>Qty</th><th>Unit Price</th><th>Amount</th></tr>
</thead>
<tbody>
${invoice.items.map(item => \`
<tr>
<td>${item.description}</td>
<td>${item.quantity}</td>
<td>${invoice.currency} ${item.unitPrice.toFixed(2)}</td>
<td>${invoice.currency} ${(item.quantity * item.unitPrice).toFixed(2)}</td>
</tr>
\`).join('')}
<tr class="total-row">
<td colspan="3" style="text-align:right">Total</td>
<td>${invoice.currency} ${invoice.total.toFixed(2)}</td>
</tr>
</tbody>
</table>
<div class="footer">
<p>Payment terms: Net 30 days. Please include invoice number in payment reference.</p>
<p>${companyInfo.bankDetails}</p>
</div>
</body>
</html>`;
}Step 3: Generate PDF via TongoRender
async function generateInvoicePDF(invoice, companyInfo) {
const html = invoiceHTML(invoice, companyInfo);
const response = await fetch('https://api.tongorender.io/v1/pdf', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
'X-API-Key': process.env.TONGORENDER_API_KEY,
},
body: JSON.stringify({
html,
format: 'A4',
margin: { top: '10mm', bottom: '10mm', left: '10mm', right: '10mm' },
printBackground: true,
}),
});
if (!response.ok) throw new Error(`PDF error: ${response.statusText}`);
return Buffer.from(await response.arrayBuffer());
}Step 4: Email Delivery
const nodemailer = require('nodemailer');
const transporter = nodemailer.createTransport({
host: process.env.SMTP_HOST,
port: 587,
auth: { user: process.env.SMTP_USER, pass: process.env.SMTP_PASS },
});
async function sendInvoiceEmail(to, invoice, pdfBuffer) {
await transporter.sendMail({
from: '"Billing" <billing@company.com>',
to,
subject: `Invoice #${invoice.number} from Company Name`,
text: `Please find attached invoice #${invoice.number} for ${invoice.currency} ${invoice.total.toFixed(2)}.`,
attachments: [{
filename: `invoice-${invoice.number}.pdf`,
content: pdfBuffer,
contentType: 'application/pdf',
}],
});
}Step 5: Putting It All Together
async function processMonthlyBilling() {
const now = new Date();
const year = now.getFullYear();
const month = now.getMonth(); // Previous month
const payments = await getMonthlyInvoices(year, month);
const companyInfo = {
name: 'Acme Corp',
address: '123 Business St, San Francisco, CA 94102',
taxId: 'EIN: 12-3456789',
bankDetails: 'Bank: First National | Account: 1234567890 | Routing: 021000021',
};
let invoiceNumber = 1001;
for (const payment of payments) {
const invoice = {
number: `INV-${year}${String(month).padStart(2, '0')}-${invoiceNumber++}`,
...payment,
dueDate: new Date(year, month, 30).toISOString().split('T')[0],
items: [{ description: payment.description, quantity: 1, unitPrice: payment.amount }],
total: payment.amount,
};
const pdf = await generateInvoicePDF(invoice, companyInfo);
fs.writeFileSync(`invoices/${invoice.number}.pdf`, pdf);
if (payment.customerEmail) {
await sendInvoiceEmail(payment.customerEmail, invoice, pdf);
}
console.log(`Processed ${invoice.number} for ${payment.customerName}`);
}
}
processMonthlyBilling().catch(console.error);Best Practices
- Idempotency — Track which invoices have been generated to avoid sending duplicates on retry.
- Error handling — Wrap each invoice in a try-catch. One failure should not stop the entire batch.
- Rate limiting — Space out API calls with a small delay to stay within rate limits during large batches.
- Storage — Always save a copy of the PDF before emailing it, in case email delivery fails.
- Tax compliance — Include all legally required fields: tax ID, sequential invoice number, itemized amounts, and applicable taxes.
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