How to Write an Invoice That Actually Gets Paid
What has to be on an invoice, why the numbering matters, the tax setting that changes what your client owes, and the small things that shorten the wait for payment.
Most advice about invoicing tells you to “be professional”. That is not the problem. The problem is that an invoice is a legal document, a payment instruction and a piece of admin all at once, and getting any one of the three wrong is what turns a two-week wait into a two-month one.
This guide covers what has to be on an invoice, why invoice numbers matter more than people expect, the tax setting that quietly changes what your client owes, and the handful of things that measurably shorten the gap between sending and getting paid. You can build one as you read using our free invoice generator — it runs in your browser and nothing you type is uploaded.
What has to be on an invoice
Rules vary by country, but the list below is what almost every jurisdiction expects, and what an accounts payable department will look for before paying you.
Two of these trip people up more than the rest.
The client as a legal entity. “Sarah at Acme” is not who owes you money — Acme Corporation Ltd is. If the name on your invoice does not match the entity in their accounting system, it can sit in a queue while somebody works out what to do with it.
Your tax number. If you are registered for VAT, GST or sales tax, your registration number is usually a legal requirement on the document, not a nicety. Your client needs it to reclaim the tax they paid you.
Invoice numbers matter more than you would think
They must be unique, and they should run in an unbroken sequence. Auditors and tax authorities pay attention to gaps, because a missing number suggests an invoice that was issued and then quietly deleted. If you are ever asked to explain your records, “I skipped a few” is a worse answer than it sounds.
There is also a presentational point. Starting at INV-0001 tells a client they are your first ever customer. Plenty of freelancers begin somewhere less revealing, or prefix by year — 2026-014 — which sorts cleanly and says nothing about volume.
Whatever pattern you pick, keep the padding consistent. INV-0099 should be followed by INV-0100, not INV-100, or your folder will sort itself into nonsense within a year.
Tax added on top, or already included
This is the setting people get wrong, and it changes what your client owes. It is worth being certain which one you mean before you send anything.
If you told the client “£120 plus VAT”, use added on top. If you told them “£120 all in”, use already included. The generator has both, and the totals update as you switch so you can see the difference before you commit.
One more case worth knowing: if some of what you supplied is zero-rated or exempt, set that rate on the individual line rather than changing the invoice-wide rate. A proper tax invoice shows each rate as its own band, and that is what your client’s bookkeeper needs.
Payment terms and the due date
“Net 30” means payment is due 30 days after the invoice date. It is a convention, not a law, and you can set whatever terms you agreed — 7, 14, 30, or due on receipt.
But write the actual date as well. “Net 30” asks the reader to do arithmetic and gives them room to argue about when the clock started. Due 13 September 2026 does neither. This is a small change that costs nothing and removes an entire category of excuse.
Agree the terms before you start the work, not when you send the invoice. Terms that appear for the first time on the bill are terms the client never accepted.
Four things that get you paid faster
Invoice the day the work lands. The payment clock usually starts when the invoice arrives, so a fortnight sitting in your drafts is a fortnight added to when the money reaches you. Month-end batching feels organised and costs you weeks.
Send it to the right place. Larger companies pay from accounts payable, not from your day-to-day contact’s inbox. Ask who invoices should go to before the first one, not after the first late one.
Make paying you trivial. Full bank details, the reference you want quoted, and the currency. Every question a client has to ask before they can pay is another week.
Reference their purchase order if they use one. In companies that issue PO numbers, an invoice without one frequently cannot be paid at all — it is not obstruction, their system simply will not match it to anything.
When it is late anyway
Assume administration before bad faith. Most late payments are an invoice sitting in the wrong inbox, a missing PO number, or an approver on holiday. A short, friendly message asking whether it reached the right person resolves more of these than a stern one.
If it is genuinely overdue, be specific: the invoice number, the amount, the date it was due, and the payment details again so nobody has to go looking. Many countries give you a statutory right to charge interest on late commercial payments — the UK’s late payment rules are one example. Mentioning that right exists is usually more effective than exercising it.
Do you need invoicing software?
Eventually, maybe. If you are sending a handful of invoices a month, a generator and a folder of PDFs is genuinely enough, and it keeps your records in a form nobody can take away or start charging you for.
The point at which paid software earns its keep is usually recurring billing, chasing automatically, multi-currency accounting, or a bookkeeper who wants everything in one system. Until then you are paying a monthly fee to avoid typing an address.
Common questions
What is the difference between an invoice and a receipt?
An invoice requests payment. A receipt confirms payment was made. Sending an invoice after you have been paid, or calling a receipt an invoice, causes real confusion in bookkeeping — they do opposite jobs.
Can I invoice without a company?
In most countries yes. Sole traders and freelancers invoice under their own name. You still need the same information on the document, and you still need to declare the income.
What if I make a mistake after sending it?
Do not edit and resend the same number. Either issue a credit note cancelling the original and send a fresh invoice, or send a clearly marked corrected version. Two different documents sharing one number is exactly the kind of thing that causes trouble later.
How long should I keep invoices?
Longer than feels necessary. Many tax authorities expect five to seven years. Whatever your country requires, the storage costs nothing and the alternative is being unable to evidence your own income.
Build one now
Our invoice generator covers everything above: the required fields, sequential numbering that keeps its padding, both tax treatments, per-line rates, discounts and deposits, twelve currencies, and your logo on the PDF. It runs entirely in your browser — your rates, your client list and your bank details never reach a server, which matters more here than on most tools.
If you need to combine the finished PDF with a timesheet or receipts, JPG to PDF will merge them into one file, and the time zone planner is useful when the client you are invoicing is in another country and you need to arrange the call about it.