How to Write an Invoice: A Step-by-Step Guide for Freelancers and Small Businesses

By The Invoice Makers team · Updated November 1, 2026 · 7 min read

To write an invoice, list your business details and your client's details, add a unique invoice number and the invoice date, itemize the work or products with quantities and prices, calculate any tax, show the total due, and state your payment terms and accepted payment methods. Then send it as a PDF and follow up if the due date passes. The rest of this guide walks through each step in detail, with a complete example at the end.

Key takeaways

• Every invoice needs a unique number, an issue date, a due date, itemized charges and a clear total.
• Specific line items and plain payment terms reduce questions and speed up payment.
• Send invoices as PDFs promptly, ideally the day the work is delivered.
• Keep a simple follow-up routine for invoices that go past due.

What is an invoice?

An invoice is a document a seller sends to a buyer requesting payment for goods or services that have been delivered or agreed. It records what was sold, how much is owed and when payment is expected. For you, it is the basis of your accounts receivable and your income records. For your client, it is the document their accounts payable team needs before they can release money.

An invoice is not the same as a receipt, which confirms a payment that has already happened. If you are unsure which document to send when, our guide to invoice vs receipt explains the difference.

Step 1: Add your business details and branding

Put your business name, address, email and phone number at the top. If you have a logo, include it; it makes the invoice instantly recognizable in a crowded inbox. Freelancers working under their own name can simply use their full name. If you have a business tax ID and your clients ask for it, add it here too.

Clearly label the document with the word "Invoice." It sounds obvious, but accounts payable departments often process documents by type, and an unlabeled page can be mistaken for a quote or statement.

Step 2: Add your client's details

Under a "Bill to" heading, write the client's company name, the name of your contact or their billing department, their address and their email. For larger clients, ask before you start work whether they need a purchase order (PO) number or a cost center on the invoice. Missing a PO number is one of the most common reasons corporate invoices get stuck.

Step 3: Assign a unique invoice number

Each invoice needs its own number that never repeats. Sequential numbers are the simplest system: INV-0001, INV-0002 and so on. Some businesses add the year (2026-014) or a client code (ACME-007) to make sorting easier. Whatever you choose, stay consistent and never reuse or skip numbers without a reason you can explain later.

For a deeper look at the options, read how to number invoices.

Step 4: Set the invoice date and due date

The invoice date is the day you issue the invoice. The due date is when payment must arrive. Show both, rather than only writing "Net 30," because a specific date removes any guesswork for the client. If you are not sure what Net 30 or Net 15 actually means in practice, our explainer on what Net 30 means covers how the days are counted.

You can work out the exact date with the payment due date calculator, which handles month lengths and weekends for you.

Step 5: Itemize the products or services

Line items are the heart of the invoice. Each line should include:

• Description: what you delivered, written so someone outside the project can understand it.
• Quantity: hours, units, days or a flat "1" for a fixed-price item.
• Rate or unit price: the price per hour or per unit.
• Amount: quantity multiplied by rate.

Vague descriptions such as "design work" invite questions. "Homepage redesign, 3 layout concepts and 2 revision rounds" does not. If you bill by the hour, track time carefully and use the billable hours calculator to total it before you write the invoice. If you have not settled on a rate yet, the hourly rate calculator can help you set one that covers your costs.

Step 6: Add subtotal, tax, discounts and the total

Below the line items, show the subtotal, then any discount, then sales tax, then the total amount due. Keeping these on separate lines makes the math easy to check.

Sales tax rules in the US vary widely. Many states tax physical goods but not most services, while some states tax certain services too, and rates often differ by city or county. Check your state and local rules, or ask an accountant, before adding tax. The sales tax calculator can do the arithmetic once you know the rate that applies.

If you received a deposit, subtract it and show the remaining balance due so the client does not pay twice.

Step 7: State your payment terms and methods

Payment terms tell the client when and how to pay. A good terms section covers:

• The due date or term (for example, "Due on receipt" or "Net 15").
• Accepted payment methods: bank transfer (ACH), check, card or a payment link.
• The details needed to pay, such as bank account information or a mailing address for checks.
• Any late fee policy you agreed with the client in advance.

Late fees are worth stating only if your contract supports them, and some states limit how much you can charge. If you do use them, the late fee calculator shows what a given rate works out to in dollars.

Step 8: Add a note and review before sending

A short line such as "Thank you for your business" is a small courtesy that clients notice. You can also add project references, a reminder of the warranty period or the contact person for questions.

Before sending, check the client name, the numbers and the due date. A single wrong digit in a bank account number can delay payment by weeks.

A worked invoice example

Here is an example invoice for a freelance web designer. The names and figures are made up for illustration.

Payment terms in this example: Net 15, payable by ACH or check. No sales tax is shown because the example assumes these services are not taxable where the designer works; your situation may differ. A ready-made web design invoice template follows the same structure if you want to start from it.

Step 9: Send the invoice

Send the invoice as a PDF, not an editable document. PDFs look the same on every device and are harder to alter. Email it to the billing contact with a short message that repeats the amount, the due date and the invoice number in the subject line, for example: "Invoice INV-2026-018 from Jordan Lee Design, due Nov 16."

Timing matters. Invoicing the same day you deliver keeps the work fresh in the client's mind. For long projects, agree on milestone or monthly billing so you are not waiting months for a single large payment.

Step 10: Follow up on unpaid invoices

A simple routine keeps follow-ups from feeling awkward:

1. A few days before the due date, send a friendly reminder.
2. On the day after the due date, send a polite note with the invoice attached again.
3. After a week or two, call or email your main contact and ask whether anything is holding up payment.
4. If the invoice is well overdue, apply any agreed late fee and consider pausing further work.

For wording you can adapt, see our guide on how to ask for payment.

Common invoicing mistakes to avoid

• Missing or duplicate invoice numbers. These cause confusion in both your books and the client's.
• No due date. "Payable soon" gives the client no deadline to plan around.
• Vague line items. Unclear descriptions lead to disputes and approval delays.
• Wrong billing contact. Sending to your project contact instead of accounts payable can add days.
• Forgetting the PO number. Many larger companies cannot pay without it.
• Math errors. Use a tool that calculates totals automatically.
• Waiting too long to invoice. The later you bill, the later you get paid.

Once you are comfortable with the basics, the freelance invoice guide covers deposits, retainers and recurring billing in more depth. It is also worth tracking what you actually earn per job; the profit margin calculator and the self-employment tax calculator help you see what is left after costs and taxes.

Write your first invoice in a few minutes

Now that you know how to write an invoice, the fastest way to put it into practice is with a tool that handles the layout and math for you. Our free invoice generator lets you add your logo, choose from 30 designs, fill in your line items and download a clean PDF, with no sign-up required. Create your next invoice now and get it in front of your client today.