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What goes on a professional invoice — and why each field matters

An invoice is a formal request for payment, and a few fields do most of the work of getting you paid on time. A unique invoice number lets both sides reference the document unambiguously in emails and accounting systems; sequential numbering (INV-001, INV-002) also doubles as a record of how many invoices you have issued. The invoice date anchors your payment terms, and the due date makes the deadline explicit rather than leaving "net 30" to interpretation. Clear bill-to details ensure the document reaches the person who can authorise payment. This tool lays all of these out in a clean preview that updates as you type, then lets you print or save it as a PDF straight from your browser.

How the totals are calculated

The math is deliberately transparent. Each line item's amount is quantity × unit price. The subtotal is the sum of every line amount. Tax is applied to the subtotal as a percentage: tax = subtotal × (rate ÷ 100), and the total is simply subtotal plus tax. All amounts are formatted to two decimal places. Worked example: two consulting days at $450 each gives a line amount of $900; add a $120 software fee line, and the subtotal is $1,020. At an 8% tax rate, tax is 1020 × 0.08 = $81.60, making the total $1,101.60. Change any quantity, price, or the tax rate and the preview recalculates instantly.

A note on where your data lives

Everything you enter stays on your own device. The tool saves your draft to your browser's localStorage, so if you close the tab and come back later, your company details, client, and line items are still there — but they are never sent to a server. This is convenient and private, with two caveats worth knowing: the data is tied to that specific browser on that specific machine, so it won't follow you to another computer, and "Clear all data" wipes it permanently. The PDF is produced by your browser's own print engine, not by us, which is why the output looks exactly like the on-screen preview.

Common use cases

• Freelancers and contractors billing by the hour or by project milestone, who need a presentable document without subscribing to accounting software.
• Small businesses issuing occasional invoices where a full ERP system would be overkill.
• One-off sales — selling a piece of equipment, sub-letting a service — where you still want a paper trail with a number and date.
• Quote-to-invoice workflows: build the line items once, save as PDF for the quote, then reuse the draft and bump the number when the work is done.

Practical tips for getting paid faster

• Be specific in descriptions. "Website work — $2,000" invites questions; "Homepage redesign + 3 revisions, 16 hrs" gets approved. Detailed lines reduce back-and-forth.
• State payment terms in the notes. Use the notes field for how to pay (bank details, accepted methods) and the consequence of late payment. The clearer the instruction, the fewer the delays.
• Set a real due date. "Due on receipt" is vague; a dated deadline gives the client a concrete target and gives you grounds to follow up.
• Save the PDF with a sensible filename. When you print to PDF, name the file with the invoice number and client so it's findable later, e.g. INV-014-AcmeCorp.pdf.

Common mistakes to avoid

• Reusing invoice numbers. Two invoices sharing a number is a bookkeeping nightmare and looks unprofessional. Always increment.
• Forgetting the tax rate field. If you are not registered to charge tax, leave it at 0 — but if you are, a blank rate silently undercharges you. Check it before sending.
• Assuming the draft is backed up. Because the data lives only in this browser, clearing browser storage or switching devices loses it. Export a PDF of anything you need to keep.
• Leaving placeholder text. Empty fields show greyed-out placeholders in the preview but they don't print as real content — fill in company and client details before generating the final PDF.