Docs · guides

Invoice generator: what must be on it

By Alberto Gulotta · Updated · 4 min read

An invoice generator is the one document tool where choosing the tool is the least important decision. Anything can lay out an invoice. What matters is whether the document contains what it is legally required to contain, because that is what decides whether it can be paid, claimed against tax, and defended later.

So this page starts with the list rather than with the products.

What an invoice must contain

The United Kingdom publishes the list plainly. Quoted from GOV.UK, read 21 August 2026.

  1. a unique identification number
  2. your company name, address and contact information
  3. the company name and address of the customer
  4. a clear description of what you’re charging for
  5. the date the goods or service were provided
  6. the date of the invoice
  7. the amount(s) being charged
  8. VAT amount if applicable
  9. the total amount owed

A sole trader must also give “your name and any business name being used” and an address where legal documents can be delivered. A limited company must use “the full company name as it appears on the certificate of incorporation”, and if it names any director it must name them all. These are the British rules — yours will differ, and the guide to writing one says where to check.

The words people use say where they are in the job. Invoice template and free invoice template come from somebody who wants a starting document. Invoice template word means they have the software already. Invoice maker and billing software are further along — a system rather than a file. Invoice format is usually somebody worried about getting it wrong, proforma invoice is a different document entirely, and receipt generator is the other end of the same transaction. Only one of those decisions has legal consequences, and it is not which tool.

Everything above is the British version, quoted from the government that publishes it. The principle is the same almost everywhere — identify both parties, describe the work, date it, number it uniquely, and state the tax — but the details are national, and a page that pretends otherwise is doing damage rather than helping.

The guide listed below is still being built. What exists today is the step-by-step of how to write an invoice and what the law requires on it, how long the copies have to be kept, according to the people who ask for them, and how to sign the finished document, and whether that signature counts.

Where to start

Five ways in, and every one of them already has a page.

“I have to send my first invoice.”
Start at How to write an invoice
“It is a receipt, not an invoice.”
Those differ, and the other end is How to organize receipts, and for how long
“How long do I have to keep the copies?”
That is How long to keep business records
“I need to sign it before I send it.”
Whether that signature counts is in How to sign a PDF, and what counts
“It has to go out as a PDF.”
The route without a converter site is in Word to PDF

The papers people confuse with an invoice, each with a different job and a different moment in the transaction.

Proforma invoiceA quote dressed as an invoice: what it is for, and why it is not a demand for payment.Being built

Not covered here. It will not give tax or legal advice. The guides here quote published rules and name the country they come from; what applies to your business depends on where you are and what you do, and that belongs to an accountant rather than to a web page.

It will not rank the invoice generators yet. That verdict needs real accounts, real invoices sent to real clients over a real month end, and a published account of what happened — a test rather than a feature list.

And it will not treat this as a design question. An invoice that looks beautiful and omits a required field is worse than a plain one that contains everything, because only one of them can be defended. What holds instead is simple: every rule quoted here names the country that publishes it.

Sources

  1. GOV.UK on what an invoice must include, sole traders, limited companies and VAT invoices — www.gov.uk, read 21 August 2026.

Written by Alberto Gulotta

Founder and editor of AI Tools Primer, writing from Palermo, Italy. Thirty-five years of taking computers apart, starting with a Commodore 64 — the long version is on the about page.

Something wrong on this page? Write to aitoolsprimer@gmail.com and it gets fixed.

Written on 21 August 2026 · last checked 9 September 2026.

Independence and limits

No affiliate links and no paid placements anywhere on this site. Nobody pays to appear here, and no company has seen this page before you did.

This is general information, not professional advice. Where a page touches money, health, safety or the law, it names its source and the date it was read — and your situation may still differ. See the privacy page and the cookie policy.