Guide

How to write an invoice: a step-by-step guide with an example

Learn how to write an invoice that gets paid: the fields to include, how to number it, which terms to set, plus a worked example and a checklist.

Updated Nov 5, 2026 · By PayToMe Editorial

Here is how to write an invoice that gets paid: put your business details and the client’s at the top, add a unique invoice number and date, list each item with a quantity and price, show the subtotal, any tax and the total, then state the due date and how to pay. Check the math before you send it.

What an invoice is for

An invoice is a request for payment. It tells a client what you did or sold, what it costs, and when and how to pay. It is also a record. The IRS lists invoices among the supporting documents, along with sales slips, paid bills, receipts, deposit slips and canceled checks, that back up the entries in your books and on your tax return.

That double role explains why details matter. A vague invoice slows the client’s approval, and a sloppy one leaves gaps in your own records. If you are not sure how an invoice differs from a receipt, read invoice vs receipt first.

The fields every invoice needs

Most invoices are built from the same handful of blocks. For a deeper reference list, see what to include on an invoice.

The word “Invoice.” Put it at the top so nobody mistakes it for a quote or a statement.
Your business name and contact details. Legal or trading name, address, email, phone. Add a tax ID or registration number if your country requires one.
Client name and billing address. Use the name of the company or person that will pay, not only the contact you work with. If the client uses purchase orders, add the PO number.
Invoice number. Unique, and in a sequence.
Invoice date. The day you issue it. Terms are usually counted from this date.
Due date. An actual calendar date.
Line items. A description, quantity, unit price and line total for each thing you are billing.
Subtotal, tax, discounts and total. Show each as its own line.
Payment instructions. How the client pays: bank transfer details, a payment link, a check address.
Terms and notes. Late payment policy, deposit already received, thank-you line.

How to write an invoice, step by step

Start from a clean template. Open a generator, a spreadsheet or a document. Add your logo if you have one, but do not spend time on design. Clear beats pretty.
Add your details and the client’s. Copy the client’s billing name and address from your agreement or their purchase order. A wrong legal name is a common reason an accounts-payable team bounces an invoice.
Assign the number and dates. Pick the next number in your sequence. Enter today’s date as the invoice date and calculate the due date from your terms. See invoice payment terms for how to choose them.
List the work as line items. One line per distinct thing. Write descriptions the client’s finance team will recognize: “Logo design, 12 hours” is better than “Design stuff.”
Do the math. Multiply quantity by unit price for every line, add the lines to get the subtotal, subtract any discount, add tax, and check the total.
State how to pay. Give one or two easy options. The fewer steps between reading the invoice and paying it, the faster it tends to be paid.
Add terms and a short note. Mention your late payment policy if you have one, and say thanks.
Review, save and send. Read it as the client would. Save a PDF copy for your records, then follow how to send an invoice.

Writing good line items

Line items are where most disputes start, so spend a minute on them.

Be specific about what was done. “Website maintenance, October 2026” is clear. “Services” is not.

Show the unit. Hours, days, items, square feet. If you bill hourly, show the hours and the rate. If you bill a fixed fee, say “Fixed fee, as per quote dated 3 October.”

Separate different kinds of charges. Labor, materials, travel and expenses belong on their own lines. A client who disagrees with one item can then question only that line instead of the entire invoice.

Reference the agreement. If a quote, contract or purchase order exists, mention its number or date. It shortens the approval path.

Do not round in secret. Use the exact quantity and price, and let the total be the sum. If you round, round at the end.

A worked example

A freelance designer, Maya Ortiz, finished a brand project for a client, Northwind Coffee. She agreed to 12 hours of logo design at 100.00 USD per hour, a flat 150.00 USD for a one-page style guide, and billed 40.00 USD for stock photos she bought on the client’s behalf. Her state charges 8.25 percent tax on the design and style guide, but not on the reimbursed photo cost, in this example. (Tax rules differ by state and service. This is illustrative.)

INV-2026-014 · Maya Ortiz Design · Net 14

Item	Qty	Amount
Logo design	12	$1,200.00
One-page style guide	1	$150.00
Tax (8.25%)		$111.38
Total		$1,461.38

The preview above shows the two taxable lines. The reimbursed stock photo cost is added below it.

Notice what Maya did. She named the client’s legal entity, gave an actual due date, separated the taxable work from the pass-through expense, and told the client what to write on the payment. None of that is difficult, and each choice removes a reason to email her with questions.

Mistakes that delay payment

No due date. Without one, the client decides when. “Due on receipt” or a date removes the guesswork.
Missing or wrong client details. If the legal name, address or PO number is wrong, an accounts-payable team may reject it.
Duplicate or skipped numbers. They make your records hard to follow and may raise questions in an audit.
Lumping everything together. A single “Project fee” line gives the client nothing to check and invites haggling.
Math errors. A total that does not add up costs you credibility. Use a calculator or a generator.
Hiding the payment method. If the client has to ask how to pay, you have added a delay.
Sending it late. An invoice that goes out two weeks after the work is an invoice that gets paid two weeks late.
Changing it after sending. If you must correct an invoice, issue a corrected one or a credit note and say so clearly. Do not quietly edit a document the client has already received.

Checklist before you send

The page says “Invoice” at the top.
Your details and the client’s billing details are correct.
The invoice number is unique and in sequence.
Invoice date and a real due date are shown.
Every line has a clear description, quantity, unit price and line total.
Tax and discounts are separate lines and the total adds up.
Payment instructions are complete and easy to follow.
Late fee policy or other terms are stated if you have them in your agreement.
A PDF copy is saved in a folder you can find later.

Where PayToMe fits

The free invoice generator is live today. It computes totals to the cent and creates a PDF in your browser. In PayToMe, now in public beta, you can also send invoices by email, take online payments, and use Via (beta), the AI assistant, to draft an invoice from a plain description of the job. Smart reminders are in development. Sign in to PayToMe to try it.

Sources

This is general information, not legal or tax advice. The statement that invoices are among the supporting documents that back up your books and return comes from the IRS page What kind of records should I keep. The IRS points to Publication 583 for more on record keeping. Tax, numbering and retention rules differ by country and state, so check with your tax authority or an accountant before relying on any example here.

Frequently asked questions

Do I need a special template to write an invoice?

No. An invoice is a document that states who is billing whom, for what, how much, and by when. A word processor, a spreadsheet or a free generator all work. What matters is that the fields are complete and the math is correct. A template just saves you from forgetting a field.

What should the invoice number look like?

Use a simple sequence you will never repeat, such as 0001, 0002, 0003, or a year prefix like 2026-014. Unique numbers make it easy for you and your client to find a document. Some countries have stricter sequence rules, so check your local tax authority if you invoice abroad.

Should I put a due date or just payment terms?

Do both. Terms such as Net 30 describe the rule, and a date such as 14 December 2026 removes any calculation for the client. A clear date is the single most useful line for getting paid on time.

Can I write an invoice before the work is finished?

Yes, if your agreement allows it. Common cases are deposits, milestone invoices and progress billing. Label what each invoice covers, for example Deposit, 50 percent of project, so the client knows which part of the total they are paying.

How long should I keep copies of my invoices?

The IRS lists invoices among the supporting documents that back up your books and tax return, but the general retention period depends on your situation and country. Ask your accountant, or see IRS Publication 583, and keep digital copies somewhere safe.

Do I have to charge sales tax or VAT on my invoice?

It depends on what you sell and where you and your client are. Rules vary by state and country. Check with your local tax agency or an accountant, and show any tax as its own line so the client can see the base amount and the tax separately.