Add PDF invoices to your app in 5 minutes

Most teams burn days wiring up headless Chrome, fighting CSS print quirks, and babysitting render servers — to produce a document whose layout never changes. An invoice API turns that into one HTTP call.

The anatomy of the call

Send your business, your customer, and the line items. Slipstack computes subtotals, discounts, and tax, lays everything out, and returns the finished PDF — synchronously.

// npm i — nothing. It's just fetch.
const res = await fetch("https://slipstack.dev/api/v1/pdf", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.SLIPSTACK_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    template: "invoice",
    data: {
      from: { name: "Acme Inc", email: "billing@acme.com" },
      to: { name: customer.name, email: customer.email },
      number: `INV-${order.id}`,
      dueDate: dueDate.toISOString().slice(0, 10),
      items: order.lines.map(l => ({
        description: l.name, quantity: l.qty, unitPrice: l.price,
      })),
      taxRate: 8.5,
    },
  }),
});
const pdfBuffer = Buffer.from(await res.arrayBuffer());
// email it, store it, or stream it to the browser

Python

import os, requests

res = requests.post(
    "https://slipstack.dev/api/v1/pdf",
    headers={"Authorization": f"Bearer {os.environ['SLIPSTACK_KEY']}"},
    json={
        "template": "invoice",
        "data": {
            "from": {"name": "Acme Inc"},
            "to": {"name": customer.name},
            "number": f"INV-{order.id}",
            "items": [
                {"description": l.name, "quantity": l.qty, "unitPrice": l.price}
                for l in order.lines
            ],
            "taxRate": 8.5,
        },
    },
)
with open("invoice.pdf", "wb") as f:
    f.write(res.content)

Common patterns

• Email on payment: generate the PDF in your payment webhook and attach it to the receipt email.
• Customer portal: render on demand — no need to store PDFs; regenerate from order data anytime.
• Branding: pass logoUrl and accentColor per tenant for white-label invoices.