How to Write an Invoice (with a Free Template)

In this article

1. What an invoice is (and isn't)
2. What to include on an invoice
3. How to write an invoice, step by step
4. How to send an invoice so it gets paid
5. Common invoice mistakes
6. FAQ

What an invoice is (and isn't)

An invoice is a formal request for payment. It tells your client what you delivered, how much they owe, when it's due and how to pay. It also becomes a record for both of you: it's how you prove income, how your client justifies the expense, and what you'll point to if a payment is late.

An invoice is different from a quote (a price offered before work starts) and from a receipt (proof that payment was already made). See invoice vs receipt for when to use each.

What to include on an invoice

There's no single federal format for invoices in the US, but clients' accounts payable teams expect these details. Missing any of them is the most common reason invoices get stuck.

1. The word "Invoice" clearly at the top.
2. Your business details: legal business name (the name on your LLC or DBA), address, phone and email. Add your logo if you have one.
3. Your client's details: company name, the contact person, and billing address. For larger companies, ask for a purchase order (PO) number and include it.
4. A unique invoice number. Use a simple sequence like INV-1001, INV-1002. Never reuse a number.
5. Invoice date and due date. The due date should match your payment terms.
6. Payment terms, such as Net 30 or Due on receipt, plus any late fee policy you agreed on in your contract.
7. Itemized line items: a clear description of each product or service, quantity or hours, rate, and line total.
8. Subtotal, discounts, sales tax and total due. Show sales tax as its own line if you collect it.
9. How to pay: ACH or wire details, a payment link, or a mailing address for checks.
10. A short thank-you and who to contact with questions.

How to write an invoice, step by step

1. Confirm the details before you start. Check the agreed price, the client's billing contact, and whether they need a PO number or a W-9 from you first.
2. Number it. Pick the next number in your sequence.
3. Describe the work specifically. "Website redesign: homepage and 4 interior pages (milestone 2 of 3)" gets approved faster than "Design services."
4. Show the math. Hours × rate, or quantity × unit price, for each line.
5. Apply tax correctly. Charge sales tax only if what you sell is taxable in the customer's state and you're registered there. The sales tax calculator lists every state's rate.
6. Set the due date from your terms, and make paying easy: include a payment link or full bank details.
7. Save it as a PDF and send it to the right person, with the invoice number and amount in the email subject line.
8. Record it in your books and set a reminder for the due date.

How to send an invoice so it gets paid

Send invoices as PDFs, not editable documents. In the email, put the invoice number, amount and due date in the subject line ("Invoice INV-1042, $2,400, due Nov 25"), address the person who approves payment, and attach the PDF. Short, specific emails get processed faster.

Timing matters too. Invoice as soon as the work is delivered or the milestone is hit. Every day you wait is a day added to when you'll get paid.

Common invoice mistakes

• Vague descriptions that make the client ask what they're paying for.
• No due date, or "payable upon receipt" buried in small print.
• Sending to the wrong person. Your project contact often isn't the person who pays bills.
• Duplicate or missing invoice numbers, which confuse both sets of books.
• Forgetting the W-9. Many US companies won't pay a new vendor until they have your Form W-9 on file.
• No follow-up. A polite reminder a few days before the due date prevents most late payments.

Frequently asked questions

Is an invoice legally binding?

An invoice on its own is a request for payment, not a contract. The binding agreement is usually your contract, signed proposal or accepted quote. The invoice is evidence of what's owed under that agreement, so keep it consistent with what was agreed.

What invoice number should I start with?

Any number works as long as each one is unique and they go in order. Many businesses start at 1001 or use a year prefix like 2026-001 so a new business doesn't look brand new.

Do I need a business to send an invoice?

No. Freelancers and sole proprietors can invoice under their own name. If you operate under a different business name, you may need to register a DBA (doing business as) with your state or county.

How long should I keep copies of invoices?

Keep them at least as long as you keep the tax returns they support. The IRS generally recommends keeping records for three years from filing, and longer in some situations.

This article is general information for US readers, not legal, tax or financial advice. Rules, prices and platform policies change, so confirm details with official sources or a qualified professional.