Payslip PDFs in Express

Why payslips become PDFs

A payslip is a personal financial record an employee keeps, uses to apply for credit, and expects to be able to open years later. That is the difference between a document and a view of a database, and it is why HR and payroll teams keep asking for this.

What a payslip has to carry

Before any of the code below matters, the template has to produce a document that is actually a payslip. These are the fields that make it one, and the ones a reader or an auditor will look for first.

• gross pay, itemised by basic, overtime and any allowances
• each deduction named separately with its own amount
• net pay, which is the number the employee checks first
• year-to-date totals for gross, tax and net
• the pay period and the payment date, which are not the same day
• the employee identifier and tax reference

Turning your whichever view engine you configured, commonly EJS or Handlebars template into a document

You already have the markup. App.render("invoice", data, (err, html) => ...) gives you it as a string, which is the only input the render needs. app.render gives you the HTML string rather than writing it to a response, which is exactly what you want here. Note it is callback-based; promisify it once rather than nesting.

The Express implementation

fetch ships with the runtime, so this adds no dependency. The render happens in a route handler that pipes the response, and you pipe the upstream body into res.

// routes/payslips.js
import { pipeline } from "node:stream/promises";
import { Readable } from "node:stream";
import { promisify } from "node:util";

const renderView = promisify(app.render.bind(app));

app.get("/payslips/:id.pdf", async (req, res, next) => {
  try {
    const payslip = await db.payslips.find(req.params.id);
    const html = await renderView("payslip_pdf", { payslip });

    const upstream = await fetch("https://api.pdfpipe.xyz/v1/pdf", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.PDFPIPE_KEY}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({
        html,
        options: { format: "A4", printBackground: true },
      }),
    });

    if (!upstream.ok) throw new Error(`render failed: ${upstream.status}`);

    // Header first, then pipe. res.send would buffer the whole document.
    res.setHeader("Content-Type", "application/pdf");
    res.setHeader("Content-Disposition", `attachment; filename="payslip-${req.params.id}.pdf"`);
    await pipeline(Readable.fromWeb(upstream.body), res);
  } catch (err) {
    next(err);
  }
});

The CSS that makes a payslip page correctly

The layout problem specific to this document is that gross, deductions and net must be visible together without scrolling or breaking, on one page, every time. These rules handle it.

/* Gross, deductions and net have to be visible together. One page,
   every time, regardless of how many deduction lines there are. */
.payslip { break-inside: avoid; }
.summary { break-inside: avoid; }

@page { size: A4; margin: 15mm; }

What goes wrong in Express

res.send on a Buffer sets Content-Length correctly but has already read the whole document into memory. res.end with no Content-Type makes the browser render the PDF bytes as text. Set the header, then pipe.

What people try first

Most Express projects reach for puppeteer, launched per request. That downloads roughly 300 MB of Chromium into your image and holds a browser process per concurrent render. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.

Where the payslip lives afterwards

Rendering is the short part. Payslips are personal financial records the employee will need for credit applications and tax filings for years. Employers commonly retain them for six years, and employees expect to be able to download an old one long after they have left.

Getting the document right

• Check net pay and the deduction breakdown, which is what an employee checks first and complains about immediately.
• Generation is triggered by a payroll run, producing every employee's document at once, so size the timeout for that path rather than for a health check.
• This is a batch shape: render the run through the batch endpoint rather than firing thousands of individual requests.
• Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.

Frequently asked

Related

Other Express documents, and the same payslip in other stacks.