How to write an invoice

An invoice is a short business document with one purpose: to get a specific amount of money moved from one party to another without anybody having to ask a follow-up question. Most of the friction in getting paid comes from invoices that leave something out, so it is worth knowing what each field is actually for.

The three jobs an invoice has to do

Before the fields, the shape. A working invoice answers three questions, and if a reader cannot answer all three in about ten seconds, the document is going to cost you time.

1. Who is billing whom? Full legal or trading names on both sides, not just a first name and a logo. The person paying often is not the person who hired you, and they need to match your invoice against a supplier record.
2. What is this for? Enough description that someone who did not attend a single meeting can see what was delivered and agree it happened.
3. How much, by when, and paid how? One unambiguous total, one date, and complete payment details. Two of the three is not enough.

The fields, one at a time

Your details

Trading name, the name of the person to contact about the invoice, an email, and a postal address. A phone number is optional but it helps if accounts payable has a question at 4pm on a Friday. If you are registered for tax, this block is normally where the registration number goes.

The client details

The entity you are billing, not the individual who briefed you, unless those are the same. Ask for the exact legal name and the billing address. A large client may want the invoice addressed to a subsidiary, and getting that wrong is a common reason an invoice is returned instead of paid. If they use purchase orders, get the PO number before you invoice, because many finance systems will not release payment without it.

Invoice number

A unique reference for this document. It is how the client refers to the payment and how you find the invoice again in eighteen months. Any consistent scheme works as long as numbers are unique and never reused. There is more detail in invoice numbering systems.

Issue date and due date

The issue date is when you are sending it. The due date is when you expect the money. Write both as real dates rather than only as a term, because “Net 30” requires the reader to do arithmetic and to guess whether you counted from the issue date or from delivery. Put the term in the notes and the resulting date in the field.

Line items

One row per thing you are charging for, each with a description, a quantity, and a rate. Quantity times rate is the line total. Use the quantity column literally: 8 hours at your hourly rate, 12 bags of coffee at the unit price, or a quantity of 1 for a fixed project fee. Resist the urge to compress a month of work into a single line called “services”, because a single opaque line is the easiest thing in the world for a client to sit on.

Subtotal, discount, tax, total

The subtotal is the sum of the line totals. A discount comes off the subtotal. Tax is then calculated on the discounted figure, not the original subtotal, which is the order almost every jurisdiction expects and the order this tool uses. The total is the number the client pays. Show all four when more than one applies. An invoice that jumps straight from a list of lines to a total invites someone to recalculate it by hand and find a difference.

Notes and payment details

This is where the invoice stops being a list and starts being payable. Bank name, account name, account number, sort code or routing number, IBAN and SWIFT for international transfers, or the payment link you use. Add the payment term and a single line of thanks, and put any PO number in the PO / reference field. If a client has to email you to ask where to send money, you have added days to your own payment cycle. See payment terms explained for wording you can reuse.

Logo

Optional, and it changes nothing legally, but a logo makes an invoice look like it came from a business rather than from a text editor. One clean image at the top is enough.

A worked example

Numbers are easier to trust than descriptions, so here is a complete invoice for a small design job. Two lines, a courtesy discount, no sales tax.

The second line is the useful one: 8 hours at $95 is $760, and showing the quantity and rate separately means the client can check the arithmetic without asking you to justify it. The discount is 10% of $3,160, so $316, which leaves $2,844.

Add sales tax and the order of operations starts to matter. At 8.5%, tax is charged on the discounted $2,844 rather than on the original subtotal: $2,844 x 0.085 is $241.74, for a total of $3,085.74. Had the tax been applied before the discount, the client would owe $26.86 more, which is exactly the kind of small discrepancy that turns into a two-week email thread.

Writing line items a client will not query

Descriptions are the part people rush and the part that causes delays. A line item is read by someone with no context, so give it some.

• Name the deliverable, not the activity. “Homepage and 4 inner page designs” is checkable. “Design work” is not.
• Include the period for recurring or hourly work. “Implementation support, August 2026” tells the reader which month they are approving.
• Reference their paperwork. A PO number, a ticket ID, or a contract reference in the description gets an invoice through an approval queue faster than anything else you can write.
• Split anything you negotiated separately. If the client agreed to a fixed fee plus expenses, show them as separate lines so a question about one does not hold up the other.
• Keep it to one line of text. Long descriptions wrap and push your totals onto a second page. Detail that runs past a sentence belongs in the notes or an attached summary.

Tax and registration numbers

This is the part that genuinely depends on where you are, and where you should not take an internet article as authority. Whether you have to charge sales tax, VAT, or GST, at what rate, and what identifiers must appear on the document are all local questions with real consequences.

What is broadly true: if you are registered, your registration number usually has to appear on the invoice, the tax has to be shown as its own amount rather than folded into the prices, and cross-border work often has different treatment from domestic work. If you are not registered, you do not add a tax line at all, and you should not imply you are. When you are unsure which applies to you, ask an accountant in your own jurisdiction once rather than guessing every month.

A last check before you send

• The client name matches the entity that will pay.
• The invoice number is new and not a duplicate of last month.
• The due date is after the issue date and is a date, not a phrase.
• Quantities and rates produce the totals you expect.
• Payment details are complete and current.
• The PO or reference the client asked for actually appears on the document.
• The file is a PDF, and you have opened it once to look at it.

Then send it to the address that pays invoices, which is often not the address of the person who hired you. Getting invoices paid on time covers the sending and following up in more detail.

Mistakes worth avoiding

• Reusing an invoice number because you copied last month’s file. Two documents with one reference is a bookkeeping problem for both sides.
• No due date, or a term with no date. An invoice without a deadline is a suggestion.
• Sending an editable file. A spreadsheet or word processor document can be altered, renders differently on the recipient’s machine, and looks provisional. Send a PDF.
• Inventing tax. Adding a tax line because it looks official, when you are not registered to collect it, is a real problem rather than a cosmetic one.
• Waiting. Payment terms start when you invoice, not when you finish the work. An invoice sent three weeks late is paid three weeks late.

If you want to see all of this assembled, the freelance invoice template shows a real example with the fields already filled in, and the invoice generator renders the PDF on your own device.