How to Write an Invoice: Step-by-Step With a Free Generator

This guide walks you through writing an invoice from a blank page to a sent PDF, field by field. Your first one takes about ten minutes; your tenth takes two. You can follow along with a spreadsheet, a Word template, or our free invoice generator, which runs entirely in your browser and needs no signup. Either way, you'll end up with an invoice a client's accounts payable team can pay without emailing you questions.

You'll need three things before you start: the client's legal name and billing address, what you agreed to charge, and your payment details. Everything else is typing.

Why the fuss over fields? Because invoices stall for boring reasons. In Intuit QuickBooks' 2026 Small Business Late Payments Report, 59% of US small businesses said they have invoices overdue by 30 days or more, and the businesses carrying unpaid invoices are owed $17.7K on average. Most of that isn't malice. It's missing details, wrong inboxes, and vague totals, all fixable before you hit send.

How do you write an invoice? The 60-second version

You write an invoice by filling in nine things: your details, the client's details, an invoice number, the issue date, a real due date, itemized lines, the tax math, the total, and payment instructions. Get those right, send it as a PDF the day the work is delivered, and you're done.

1. Put your business details at the top
2. Add the client's name and billing address
3. Assign a unique invoice number
4. Date it, and write the actual due date
5. Itemize the work: description, quantity, rate, amount
6. Show the math: subtotal, tax, total due
7. State payment terms and how to pay you
8. Send it as a PDF to whoever processes payments

That's the whole job. The rest of this guide is each step done properly, with the wording, worked numbers, and traps that decide whether an invoice gets paid on the due date or parked in a clarification queue.

What should an invoice include?

An invoice is a dated, itemized request for payment: it tells your client what they're paying for, how much they owe, and when the money is due. Nine fields cover all of that. Skip one and you hand the client a reason to wait.

A note on 'required': no US federal law mandates an invoice layout, but your client's accounts payable system effectively does. Most AP software, the Bill.com and Coupa class of tools, auto-rejects bills with no number, no due date, or no remittance details. VAT-registered sellers in the UK and EU have stricter statutory fields on top. We go field by field, country by country, in what to include on an invoice.

What does a finished invoice look like?

Here's a complete invoice for a fictional copywriting project, billed March 1, 2026 on net 30 terms. Every number adds up, which is exactly what your client's software checks:

The full page would also carry Brightline Design's name, address, and bank details, Northpeak Foods' billing address, invoice number 2026-014, and the issue date. Nothing on it needs explaining. That's the standard to aim for.

Step 1: Put your business details at the top

Start with who you are: your business name (or your own legal name if you're a sole proprietor), address, email, and phone. If you have a tax ID that belongs on invoices in your country, such as an EIN in the US or a VAT number in the UK or EU, add it here. This block does two jobs: it tells the client who to pay, and it makes the document identifiable months later when someone audits a card statement. Add your logo if you have one; skip it if you don't.

The trap to avoid: billing under a nickname or a trading name the client's finance team won't recognize. The name on the invoice should match the name on the contract and, ideally, the name on your bank account. Mismatches get invoices bounced back for 'vendor verification', which is a polite way of saying your payment just fell out of the queue.

Freelancing under your own name? That's normal and legal in most places. Our guide to invoicing as a freelancer covers the tax ID question in detail.

Step 2: Address it to the person who actually pays

Next, the client block: company name and billing address, plus a contact name. Here's the part people get wrong. Your day-to-day contact approves the work; the person who pays might be their office manager, an accounts payable clerk, or an outsourced bookkeeper. Ask once, on the first project: 'Who should invoices go to?' Write that name and email on the invoice itself, for example 'Attn: Accounts Payable, Northpeak Foods'. It saves your contact from forwarding it, which is where invoices go to nap.

One question to ask any mid-size or large client before the first invoice: 'Do you need a PO number on it, and do I need to register in your vendor portal?' Companies running Coupa, SAP Ariba, or Bill.com often can't pay an invoice that doesn't match a purchase order, and vendor onboarding can take days. Ask during the project, not after. And if the company's registered office differs from where your contact sits, invoice the registered or billing address.

Step 3: Give it a unique invoice number

Every invoice gets its own number. No duplicates, no reuses. The simplest scheme that survives tax season is year-prefixed and sequential: 2026-001, 2026-002, and so on. Gaps stand out immediately, which your accountant will appreciate, and clients can reference the number when they pay. One vanity tip that costs nothing: start at 1001 instead of 1, so your tenth invoice doesn't announce that it's your tenth. More schemes in our guide to invoice numbers.

Put the number somewhere obvious: top right, next to the dates, labeled 'Invoice number' so nobody confuses it with a PO number or a customer ID.

Watch out for this one: deleting a mistaken invoice and reusing its number. If you're VAT-registered in the UK or EU, sequential, gap-free numbering is a legal requirement, not a preference. Void the bad invoice and issue a corrected one with a new number instead.

Step 4: Date it, and write the actual due date

Two dates go on every invoice: the issue date (the day you send it) and the due date. Write the due date as an actual calendar date, 'Due March 31, 2026', not just 'net 30'. Terms like net 30 are fine as supporting detail, but AP clerks schedule payments by date. A date gets scheduled; a vague term gets read later. 'Due on receipt' sounds urgent and gets ignored. We'd never send an invoice without a real date on it.

Worked example: you deliver and invoice on March 1, 2026 with net 30 terms. The clock runs from the invoice date, so payment is due March 31, 2026. Write both lines on the invoice: 'Payment terms: net 30. Due date: March 31, 2026.' Now nobody has to do calendar math to pay you.

Step 5: Itemize the work you're charging for

Each line needs four things: what you delivered, the quantity, the rate, and the line amount. 'Consulting services, $2,000' forces the client to reply with questions. 'Homepage rewrite, 8 pages at $120 each, $960.00' answers them before they're asked. The test we use: could someone in the client's finance team who has never met you, never joined a project call, and never read your proposal look at this line and know exactly what the money bought?

Hourly work gets the same treatment: 'Development, March 2 to 13: 22.5 hours at $95 = $2,137.50.' Fixed-price project? One line per deliverable still beats a single lump sum, because it shows what the money bought and gives you a per-piece record if the scope grows.

Another trap: dumping reimbursable expenses into one 'Expenses: $430' line. List each expense with its date and keep the receipts. Plenty of corporate AP teams won't reimburse anything without item-level detail.

Billing across borders? State the currency in the header and again on the total. An 'all amounts in USD' line stops a European client from accidentally paying you the same number in euros.

Step 6: Show the math: subtotal, tax, and total

Below the lines, show a subtotal, then each tax or discount on its own line, then the total due as the biggest number on the page. If you charge sales tax or VAT, show the rate and the amount separately: 'Subtotal $1,360.00, VAT 20% $272.00, total due $1,632.00.' Client software often checks that lines plus tax equal the total, and a one-cent rounding error can hold an invoice in a queue. Round per line, then add. If you'd rather not do the math by hand, the generator totals everything as you type.

Discounts get their own line too, written as a negative: 'Early-payment discount, 2% if paid by March 11: -$27.20.' What trips people here is guessing about tax. Whether you should charge sales tax or VAT depends on your country, your client, and what you sell, and we can't tell you your local rules. If you're not registered, say so in one short line: 'No VAT charged, not VAT registered' does the job.

Step 7: Set payment terms and say how to pay you

Payment terms are the rules of the debt: how long the client has and what happens after that. Net 14 and net 30 are the workhorses for freelancers and small businesses. Net 60 shows up when you bill large companies whose AP cycles run monthly. Agree on terms at the quote stage so nothing on the invoice is a surprise, then spell out how to pay: bank details for transfers, a card link if you use Stripe or PayPal, a mailing address for checks. Every question you answer here is a day off the wait.

For the full menu, including net 15 versus net 30, early-payment discounts like 2/10 net 30, and when each makes sense, read our invoice payment terms guide.

Step 8: Send it as a PDF, to the right inbox, the same day

Send the invoice the day the work is delivered or the milestone is hit. Waiting until month-end is an interest-free loan you're giving a client who didn't ask for one. Attach a PDF, not a Word file, which edits easily and opens badly on phones, and name it something searchable like invoice-2026-014-brightline.pdf. Address it To the person who pays, CC your project contact, and keep the email short.

If the client uses a vendor portal, upload the same PDF there as well: the email is the courtesy, the portal entry is the payment trigger. And one habit worth building: if the due date passes, reply to your own sent email. The invoice stays attached to the thread, and the reminder costs you two lines.

What mistakes get invoices ignored?

We've looked at a lot of stalled invoices while building this tool. The slowest ones tend to share five problems, and all five are free to fix.

• Vague lines. 'Services rendered, $3,000' makes someone email you for detail. Detail is the job: write what was delivered, when, and at what rate.
• No real due date. 'Due on receipt' and 'ASAP' don't get scheduled by any AP system. A calendar date does.
• The wrong inbox. Your project contact forwards it to finance a week later, if you're lucky. Find the payer and copy them from the start.
• Surprise totals. A total that doesn't match the quote kills trust instantly. If the scope grew, send a revised quote before the invoice.
• Sending weeks late. The client's memory of your value fades fast. Invoice the day you deliver; the work is never worth more than it is on that day.

The invoices that get paid slowest are the ones that make someone ask a question. Every question costs about a week.

— Invvy Editorial Team

How long should you keep invoices?

Keep every invoice you send, paid or not. Retention rules come from tax authorities and vary by country, so treat these as minimums and check your local rules:

Our rule of thumb: keep everything seven years as PDFs named by invoice number. Storage is cheap. Reconstructing a 2026 invoice in 2031 isn't.

Before you hit send: the 30-second checklist

Run this over every invoice before it leaves your hands. It catches everything on this page faster than re-reading the guide:

• Client name and billing address match the contract
• Invoice number is unique and in sequence
• Issue date, plus a due date written as a real date
• Every line has a quantity, a rate, and an amount
• Subtotal, tax, and total agree to the cent
• Bank details or a payment link are on the page
• PDF format, searchable filename, sent to the person who pays

Print it, or keep it as a note on your desk. Five invoices from now it's muscle memory.