An invoice is an instruction, not a summary
The document exists to get money moved. Everything on it either helps the person paying take that action or it is decoration. That framing settles most arguments about what an invoice should look like, because the reader is rarely the person who hired you — it is someone in accounts who has never heard of the project and has forty other documents to process this morning.
What they need is: who is billing, who is being billed, what for, how much, by when, and how to pay. An invoice missing any of those does not get queried, as a rule. It gets set aside.
What an invoice normally has to carry
Requirements differ by country and by whether you are registered for a sales tax, so check what your own tax authority asks for rather than taking a general list as gospel. That said, most jurisdictions expect broadly the same things:
- A unique invoice number, in a sequence with no gaps.
- The issue date, and usually a due date or stated terms.
- Full details of both parties — trading name, address, and any tax registration number that applies.
- A description of what was supplied, with amounts.
- Tax shown separately, where you charge it.
- Payment details: bank account, reference to quote, or the payment link you use.
A simple generated invoice gives you a company name, a client name, priced line items, today's date, a generated invoice number and a total. That covers a good part of the list and not all of it. The gap is easy to close: put the due date, your payment details and any tax registration into line items of their own, or into the company name entry, so they appear on the page rather than being remembered later.
Write line items that do not get queried
One line per deliverable, described the way the client's own paperwork describes it. If they raised a purchase order calling it "Website — Phase 2", bill it as "Website — Phase 2", not "design work". Matching wording is what lets accounts approve it without going back to the person who commissioned it, and that single round trip is often the whole delay.
Where the work was hourly or sold by the unit, put the number in the quantity field and the price per unit in the rate field rather than folding both into the description — the amount is worked out for you, and a total with the working shown next to it invites fewer questions than one without.
A row per item, and a shortcut for a long list
Each item is its own row: a description, a quantity and a rate. The amount is quantity multiplied by rate, worked out as you type rather than typed itself, so there is nothing to get wrong there and nothing to re-add if a rate changes.
Quantity defaults to one, which is correct for most flat-fee lines and can be left alone. Set it when the line is genuinely billed per hour, per unit or per item — "6" hours at a rate of "45" reads as 6 on the invoice and totals 270, rather than needing "6 hours at 45" spelled out in the description.
Adding rows one at a time is fine for a short invoice. For a long one, paste a multi-line list into any description field and each line becomes its own row: "description, rate" if every line is one unit, or "description, quantity, rate" where quantities vary. It is the same shape the tool used before quantity existed, so a list kept from an old invoice still pastes in correctly.
Currency and tax are yours to state
Two things are not calculated for you, and both cause disputes when they are assumed.
The currency symbol is a setting, not a fixed dollar sign — pick the right one before generating. It still is not stated in words anywhere on the page, so a line item reading "All amounts in EUR" removes any doubt, and is worth adding even when you think the client knows.
Tax is not worked out or added. The total is the sum of the lines as entered. If you charge VAT, GST or a sales tax, either enter tax-inclusive amounts and state that clearly, or add the tax as its own line item so the figure is visible. A client who pays a total that turns out to have excluded tax will not enjoy the second invoice.
Number them, and keep them
Sequential numbering is not bureaucracy. It is how you find the invoice again when the client says they never received it, how your accounts reconcile against your bank, and how an auditor confirms nothing is missing. 2026-014 or ACME-0031 both work; what matters is that the sequence is unique and unbroken.
Save every invoice you issue, as the PDF you actually sent. [msm_tool slug="pdf-invoice"] writes a real PDF with a download link — A4, US Letter and A3 keep the usual layout at their own size, and the two thermal-roll widths switch to a receipt layout instead of shrinking a sheet that would no longer fit.
Before you send it
Read the total first, then the client's name, then the total again. Those are the two fields that cause an invoice to be rejected outright, and the total is arithmetic done on whatever you actually typed rather than what you meant.
Send the PDF rather than an editable document, address it to the accounts contact rather than the person who briefed you, and put the invoice number in the subject line. Then diarise a polite follow-up for a week after the due date, because invoices are not usually refused. They are forgotten.