Updated October 18, 2026
To create an invoice, add your business and client details, assign an invoice number, describe the work, enter quantities and prices, show the total and due date, then send the checked document to your client. You can use a spreadsheet, a document template or a dedicated invoice generator.
This guide uses a fictional $300 design job to show what to write, how the totals work and what to check. To make your own PDF while following along, open CatInvoice's free invoice generator. No account or watermark is required.
What should you put on an invoice?
- Sender: your business or trading name and contact details.
- Client: the customer's name and billing details.
- Invoice number: a unique reference, such as INV-2026-0042.
- Dates: the invoice date, payment due date and service period if relevant.
- Work or products: descriptions, quantities, rates and line totals.
- Totals: subtotal, applicable tax, agreed discounts, shipping, payments already received and remaining balance.
- Payment instructions: the agreed method, the details needed to pay and the invoice number as the reference.
- Client references: a purchase-order number or project reference if required.
See what an invoice means for an explanation of the document. Required details depend on your location and business. For a regional example, GOV.UK lists the information required on UK invoices.
How to create an invoice in six steps
1. Choose a format your client can open
A PDF keeps the layout consistent for your client. Start from a document or spreadsheet template, or use an invoice generator to calculate totals and prepare the document. In CatInvoice, choose Classic, Modern or Bold for different layouts using the same invoice details. Browse invoice templates for more design options.
2. Add your details and the client's billing information
Enter your business or trading name, contact information and client name. Use the billing details the client provided. For an organization, ask whether the invoice needs a particular company name, billing address, purchase-order number or contact. A logo is optional; accurate names and payment details matter more.
3. Set the invoice number, issue date and due date
Use a unique invoice number so you can identify the bill later. Choose a sequence you can maintain; INV-2026-0042 is an example, not a required format.
The invoice date records when the document is issued. The due date gives the payment deadline under your agreement. An October 18, 2026 invoice with Net 15 terms is due November 2, 2026. Check your own deadline with the invoice due date calculator.
4. Describe each service or product and its agreed price
Use a separate line for each charge the client needs to recognize. “Logo design refinements — October project” is clearer than “Design work.” Use the units you agreed: hours, items, sessions or a fixed project fee. For an hourly line, multiply hours by the hourly rate. For a fixed project, use a quantity of one and the project fee.
5. Check the total, deposit and balance due
Add the line totals, then apply the appropriate tax, agreed discount or shipping charge. Subtract payments already received once. The remaining balance is the amount still requested. CatInvoice updates totals as you edit; check that you entered the correct amounts and currency.
6. Add payment instructions, review and export
Write the agreed payment method, instructions and reference in your notes or terms. Include a clear deadline rather than only “Net 30.” Adapt these payment terms examples if you need wording.
Review the full preview, download the PDF or use browser printing. Download and attach the PDF yourself when emailing it; CatInvoice does not email the attachment from its servers.
A complete example: freelance design invoice
Northstar Studio is billing Cedar & Co. for design work. These names and prices are fictional, in US dollars, with no tax, shipping or discount.
- Invoice number: INV-2026-0042
- Invoice date: October 18, 2026
- Payment terms: Net 15
- Due date: November 2, 2026
| Description | Quantity | Rate | Amount |
|---|---|---|---|
| Logo design refinements | 2 hours | $75 | $150 |
| Social graphics | 3 deliverables | $50 | $150 |
| Subtotal and total | $300 | ||
| Deposit received | $100 | ||
| Balance due | $200 | ||
The calculation is (2 × $75) + (3 × $50) = $300. Subtract the $100 deposit and the client owes $200.
Payment of the remaining $200 is due by November 2, 2026. Please pay by the agreed bank transfer method using INV-2026-0042 as your reference.
What to say when you send the invoice
Attach the checked PDF, send it to the billing contact and keep the message specific:
Subject: Invoice INV-2026-0042 — design work
Hi, I've attached the invoice for the logo refinements and social graphics. The remaining balance is $200, due November 2, 2026. Payment details are on the invoice. Let me know if your billing team needs anything else. Thanks!
Keep a copy and note when it was sent. When the client pays, record the payment against the same invoice number.
Common invoice mistakes to catch before sending
- Reusing an invoice number for unrelated work.
- Using a vague service description or omitting the billing period.
- Choosing the wrong currency, quantity or rate.
- Requesting the full total after a deposit has been received.
- Writing a payment term without an actual due date.
- Omitting a purchase-order number the client requested.
- Forgetting the attachment or sending it to the wrong contact.
Save a record you can find again
Use the invoice number and client name in your file name. Keep the invoice, payment notes and corrections together. Our invoice record-keeping guide explains a simple filing routine.
CatInvoice's saved records stay in the current browser, with no automatic account sync. Download PDFs and export a JSON backup before clearing browser data or changing devices. For repeat billing, reuse saved details or duplicate an invoice, then review the new dates and amounts.
Frequently asked questions
Can I make an invoice myself?
Yes. Use a document, spreadsheet or invoice generator, include the details required for your location and business, and check the numbers before sending.
How do I create an invoice for free?
Open CatInvoice, enter your business and client details, add the work and prices, review the total and download the PDF. No account or CatInvoice watermark is required.
Is an invoice the same as a receipt?
No. An invoice requests payment or records a charge. A receipt acknowledges payment received. Sending an invoice does not confirm the client has paid.
Can CatInvoice collect payment for me?
No. You provide your own payment instructions. CatInvoice prepares the document but does not process payments or reconcile your bank.