Document tools

What an invoice has to include

A usable invoice identifies both parties, gives every line item a description, a quantity, and a unit price, and states the total without ambiguity. Most jurisdictions also expect a unique invoice number, an issue date, and a due date.

Tax and discounts are where hand-built invoices usually go wrong. A percentage discount applied before or after tax produces a different total, so the order of calculation has to be deliberate. This tool applies the discount to the subtotal first, then calculates tax on the discounted amount.

• Invoice number, issue date, and due date
• Both parties, with registration or VAT details where required
• Line items with quantity and unit price
• Subtotal, discount, tax, and the final total
• Payment terms and bank details in the notes field

Why the totals are computed in cents

Floating point arithmetic cannot represent most decimal amounts exactly. Adding 0.1 and 0.2 in JavaScript returns 0.30000000000000004, and while that looks harmless on a single line it accumulates across a long invoice until the printed total disagrees with the sum of its parts.

Every amount here is held as an integer number of the smallest currency unit and converted to a display string only when it is rendered. Rounding happens once, at the end, so the figure on the page is the figure that was calculated.

Printing, and where your data lives

The invoice renders to a print view, so the browser's own print dialog produces the PDF. Nothing is rasterised by a third-party service and there is no watermark to work around.

Drafts autosave to this browser's local storage, so a refresh does not lose your work. The same property cuts the other way: the data exists only on this device, which makes it convenient but not a backup.