What actually has to be on an invoice
The fields a client's accountant looks for, the ones a tax inspector looks for, and the handful that get invoices sent back unpaid.
An invoice is not a letter asking to be paid. It is a record two businesses and at least one tax authority will read separately, months apart, without being able to ask each other what was meant. Almost everything on the list below exists because somebody once left it off.
The five that are never optional
- A unique number that never repeats and never goes backwards. Skipped or reused numbers are the first thing an inspection asks about, because they are how a missing sale hides.
- The date it was issued — and, separately, the date payment falls due. "30 days" written in the terms is not a date.
- Both parties in full: legal name, address, and tax registration number wherever one applies. Not a trading name, not an email address.
- One line per thing you are charging for, with the quantity, the unit price and the tax rate shown separately rather than folded into a single figure.
- The total, broken into net, tax per rate, and the amount actually payable.
That last one is where most spreadsheets quietly fail. If a document carries two tax rates and a discount across the whole invoice, the discount has to be allocated between those rates — and the allocation has to come out to the last cent, or the breakdown stops adding up to the total. That is arithmetic worth having done for you: the invoice generator works the totals out server-side and prints the breakdown line by line.
The ones that depend on where you are
Beyond the five, every country adds its own. A French invoice has to carry late-payment penalties and the €40 recovery indemnity, and — if you are in franchise en base — the article of the tax code that exempts you. A Moroccan invoice needs the ICE of both parties, and it is the number most often missing when one comes back rejected. A US invoice generally carries no sales tax at all on services, but does need the EIN your client will report against.
The ones nobody demands but everybody wants
- How to pay you — IBAN, ACH details, or the address a cheque goes to. An invoice without payment details is an invoice that gets replied to instead of paid.
- A reference the client can quote back: their purchase order, or your quote number.
- What has already been paid, and what is left. A deposit that goes unrecorded is a deposit somebody will argue about.
- A subject line in plain words. "Website redesign, phase two" saves the person approving it from opening the attachment.
None of that is difficult. It is just easy to forget under time pressure, which is why it is worth filling in once and letting the form remember it.
