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How to write an invoice

An invoice is a formal request for payment — it needs to be clear enough that your customer knows exactly what they owe, why, and how to pay it, and complete enough to hold up as a business record. Here's what every invoice needs and how to put it together.

1. Start with a unique invoice number

Every invoice you send should have a unique identifier, both so you can track which invoices are paid and so your customer's accounts payable team can reference it. A simple sequential scheme works fine (INV-1001, INV-1002...), or you can prefix by year (2026-001) if you send a high volume. Whatever scheme you pick, don't reuse a number — it makes bookkeeping and, in many jurisdictions, tax compliance harder.

2. Add your business details

Include your business name, address, email, and phone number. If you're VAT/GST registered or have a tax ID, include it — many business customers need it to process payment, and it's required on tax invoices in most jurisdictions. If you have a logo, this is the place for it; it makes the document look intentional rather than improvised.

3. Add your customer's details

Include the customer's name (or company name), billing address, and — if different — a shipping address. Get the legal entity name right; a payment sent to the wrong department or entity can stall for weeks.

4. Include the issue date and due date

The issue date establishes when the invoice was created; the due date tells the customer when payment is expected. Common terms are "Net 15," "Net 30," or "Due on receipt" — state the actual date rather than only the term, so there's no ambiguity.

5. List your line items clearly

Each line item should have a description specific enough that the customer recognizes what they're paying for, a quantity, a rate, and the resulting amount. For hourly work, include the hours and hourly rate rather than a single lump sum — it builds trust and heads off disputes. For products, a SKU or product code helps if the customer needs to match the invoice against a purchase order.

6. Apply tax correctly

If you charge sales tax, VAT, or GST, show the rate and the resulting tax amount as a separate line, not folded into the item prices. If you're dealing with multiple tax rates (for example, different rates for different products, or a compound tax on top of another), list each one so the customer can verify the math. See our guide to calculating sales tax on an invoice for the mechanics.

7. Show subtotal, discounts, and total clearly

Lay the math out in order: subtotal, any discount applied, tax, shipping or other charges, then the total. If the customer has already paid a deposit, show it as a credit against the total so the "balance due" figure is the actual amount still owed.

8. Include payment instructions

State exactly how you want to be paid — bank transfer details, a payment link, check-by-mail address, or whatever methods you accept. Ambiguity here is one of the most common causes of late payment; if the customer has to email you to ask how to pay, you've already added days to your payment cycle.

9. Add notes and terms if relevant

A short thank-you note is good practice. If you charge late fees or have specific terms (return policy, warranty period, project scope reference), state them briefly on the invoice itself rather than assuming the customer remembers a separate contract.

Common mistakes to avoid

• Reusing invoice numbers — always increment, never duplicate.
• Vague line items — "Services rendered" invites questions; "Website redesign — homepage and 4 interior pages" doesn't.
• Missing due date — "payment due upon receipt" without a stated date still leaves room for confusion.
• Folding tax into item prices — always break it out as its own line.
• No payment instructions — the single most avoidable cause of delayed payment.

Invoice payment terms, decoded

Payment terms are usually written as shorthand that isn't always obvious if you haven't seen it before. Here's what the common ones actually mean:

• Due on receipt — payment is expected as soon as the customer receives the invoice, with no grace period. Common for smaller amounts or one-off work.
• Net 15 / Net 30 / Net 60 — payment is due that many days after the invoice date (not the delivery date, unless you state otherwise). Net 30 is the most common default in B2B billing.
• 2/10 Net 30 — a small early-payment discount notation: a 2% discount if paid within 10 days, otherwise the full amount is due in 30. Less common outside traditional wholesale/manufacturing billing, but worth knowing if a client uses it.
• EOM (End of Month) — payment due by the end of the month the invoice was issued in, regardless of the exact issue date.
• 50% upfront, balance on delivery — not a single-invoice term but a two-invoice structure: a deposit invoice, then a final invoice showing the deposit credited against the total (see step 7 above).

Whichever term you use, always print the literal due date on the invoice as well — "Net 30" printed alone still makes the customer do arithmetic, and it's one more place for a date to get miscounted.

A complete example, put together

Put together, the 9 steps above look like this — a freelance web design project, assembled into one invoice:

Notice what makes this work: the invoice number and dates are unambiguous, each line item is specific enough to recognize, tax is broken out rather than folded in, and the previously paid deposit is shown as a credit so "balance due" is the actual amount still owed — not the full project value again.

Digital vs. paper invoices

A PDF sent by email (or generated by an online tool) has effectively replaced paper invoicing for almost every use case — it's faster to send, easier for the customer to file and search, and doesn't get lost in transit. A Word or Excel template exported to PDF works, but tends to drift out of formatting consistency over time as different people on your team edit it, and doesn't check your math. Handwritten or carbon-copy paper invoice pads still show up in a few trades (some in-person service calls), but they're the exception now, not the norm, and offer no easy way to keep a searchable digital record. Unless a specific client or jurisdiction requires paper, a clean PDF is the default choice.

If this isn't a one-off: recurring and phased billing

Not every invoice stands alone. If you bill the same client on a regular schedule (a monthly retainer, for example), a recurring invoice keeps the format consistent and just updates the date and any variable line items each cycle — clients get used to the layout, which speeds up their own approval process. If you're billing a single project across several stages, a milestone or progress invoice should reference the total project value and show what's been billed to date, not just the current invoice in isolation, so the client can track the running total against the agreed scope.

Questions people ask before sending their first invoice

What's the minimum an invoice legally needs to include?

Requirements vary by jurisdiction, but almost everywhere that's at minimum: your business name and contact details, the customer's name, a unique invoice number, an issue date, a description of what was sold, and the amount due. VAT/GST-registered businesses in most countries also need to show their tax registration number and the tax breakdown as a separate line. Check your local tax authority's specific requirements if you're registered for VAT, GST, or sales tax.

Do I need to sign an invoice?

Not usually. Unlike a contract, an invoice is a record and a payment request, not an agreement being formed — most invoices are valid without a signature. Some industries or specific clients may still request one; if so, a typed name or a simple e-signature is normally sufficient.

Can I invoice in a currency other than my own?

Yes, and it's common for international clients — just state the currency explicitly (an amount without a currency code is ambiguous) and be aware that exchange-rate fluctuations between the invoice date and payment date are usually the paying party's risk, not yours, unless you've agreed otherwise.

What should I do if a client disputes an invoice?

Respond promptly and specifically — ask exactly which line item or amount they're disputing rather than letting the whole invoice sit unpaid over one questioned line. If the dispute is legitimate, issue a credit note for the corrected amount rather than editing and resending the original (see our guide on invoices vs. receipts for how credit notes fit in). If it isn't, point to the agreed scope or contract that supports the original amount.

How long should I keep copies of invoices I've sent?

This depends on your jurisdiction's tax and business record-keeping rules — many countries require 5–7 years for business records, some longer. This isn't tax advice; check the specific retention period that applies to your business, and keep both the PDF you sent and a note of when it was paid.

Make one now

Our free invoice generator handles all of the above automatically — the fields, the math, and the layout — so you can focus on getting the details right instead of the formatting.

Create Your Invoice