Writing a professional invoice isn't complicated — but getting it wrong can delay your payment by weeks. This guide walks you through every field you need to include, the right format to use, and how to send it so clients pay you on time.
Quick tip: If you just need to create an invoice right now, use our free invoice generator — no signup, no watermark, instant PDF download.
What is an Invoice?
An invoice is a formal document you send to a client after completing work, requesting payment for your services or products. It creates a legal record of the transaction and specifies the amount owed, payment terms, and due date.
A proper invoice protects you legally, helps you track income, and makes it easier to follow up on unpaid work.
What Every Invoice Must Include
Most countries don't prescribe a rigid invoice format, but there are 10 fields that every professional invoice should have:
| Field | Description |
|---|---|
| The word "Invoice" | Makes it clear this is a payment request, not a quote or receipt |
| Invoice number | A unique reference like INV-001 — helps both parties track it |
| Invoice date | The date you issued the invoice |
| Due date | When payment is expected — typically Net 15, Net 30, or a specific date |
| Your business details | Name, address, email, and phone number |
| Client details | Client name, company, and billing address |
| Line items | Each service or product with description, quantity, and unit price |
| Subtotal | Total before tax or discounts |
| Tax (if applicable) | VAT, GST, or sales tax — depends on your jurisdiction |
| Total due | The final amount the client owes you |
How to Write an Invoice: Step by Step
Add your business information
Include your full name (or business name), address, email address, and phone number at the top. If you're a registered business, add your registration number or tax ID. This lets the client know who the invoice is from and how to reach you if they have questions.
Add the client's information
Include the client's full name or company name and their billing address. For larger companies, find out which department handles accounts payable — billing to the wrong department is a common reason invoices get delayed.
Set an invoice number and dates
Give every invoice a unique sequential number (INV-001, INV-002…). This makes it easy to reference in emails and follow-ups. Set today as the invoice date and add a clear due date — Net 30 (30 days from invoice date) is standard for most freelancers.
List your line items clearly
Each service or deliverable should be its own line item. Be specific — "Logo design, 3 revisions" is better than just "Design work." Include the quantity, unit price, and line total. Vague descriptions cause clients to ask questions before paying.
Add tax and calculate the total
If you're required to charge VAT, GST, or sales tax, add it as a separate line. Show the subtotal, tax amount, and final total clearly. Transparency here avoids disputes later.
Include payment instructions
Don't make clients guess how to pay you. In the notes section, specify your preferred payment method — bank transfer (include account details), PayPal, Stripe, check, etc. The easier you make it to pay, the faster you get paid.
Download as PDF and send
Always send invoices as PDF, not Word or editable files. PDFs look professional, can't be accidentally edited, and render correctly on any device. Email the PDF directly to your client's accounts payable contact.
Invoice Payment Terms Explained
Payment terms tell the client when you expect to be paid. Here are the most common ones:
- Due on receipt — Payment expected immediately upon receiving the invoice
- Net 15 — Payment due 15 days after invoice date
- Net 30 — Payment due 30 days after invoice date (most common)
- Net 60 — Payment due 60 days after invoice date (common with large corporations)
- 50% upfront — Deposit before work starts, remainder on completion
Pro tip: Research shows invoices with "Net 7" or "Due in 7 days" get paid significantly faster than "Net 30." For new clients, start with shorter terms and extend once trust is established.
5 Mistakes That Delay Payment
- No due date — Clients treat invoices without due dates as optional. Always include one.
- Wrong contact — Sending to the client's personal email instead of accounts payable slows things down.
- Vague line items — "Consulting services — $2,000" invites pushback. Be specific about what was delivered.
- Missing payment details — If they can't figure out how to pay you, they won't.
- No follow-up — Send a friendly reminder 3 days before the due date, then the day it's due.
Invoice Example
Here's what a well-written invoice looks like in practice:
123 Main St, London EC1A
hello@acmestudio.com
#INV-042 · 12 Mar 2026
Due: 11 Apr 2026
| Description | Qty | Rate | Total |
|---|---|---|---|
| Website redesign — 5 pages | 1 | $2,400.00 | $2,400.00 |
| Logo design — 2 concepts, 3 revisions | 1 | $600.00 | $600.00 |
| Monthly maintenance (March) | 1 | $200.00 | $200.00 |
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Open Free Invoice Generator →Frequently Asked Questions
Do I need to be a registered business to send an invoice?
No. Freelancers and sole traders can send invoices using their personal name. You don't need a registered business or company number. Just include your name, address, and contact details where the "business" information goes.
What format should I send my invoice in?
Always PDF. Word documents and spreadsheets look unprofessional, can be accidentally edited, and sometimes don't display correctly on the recipient's device. PDF is the universal standard for invoices.
What if my client doesn't pay on time?
Send a polite reminder email 3 days after the due date. If there's still no response after 7 days, send a firmer follow-up referencing the invoice number and original due date. Most late payments are due to invoices getting lost in inboxes rather than deliberate non-payment.
Should I charge late payment fees?
You can include a late payment clause in your notes section (e.g., "1.5% monthly interest on invoices unpaid after 30 days"). Whether you enforce it depends on the client relationship — but having it written on the invoice often encourages timely payment on its own.