How to invoice a client: a complete guide for freelancers
Invoicing a client is how you turn completed work into cash in the bank. A good invoice is clear enough that accounts can approve it quickly, specific enough that nobody argues about what was delivered, and professional enough that clients take you seriously.
This guide covers what to include, how payment terms work, how to send invoices, what to do when payment is late, and tools that make the process faster.
Quick answer
A client invoice should include your business details, the client’s billing details, a unique invoice number, the invoice date, a payment due date, line items that describe the work, the total due, payment instructions, and payment terms. Send it promptly after delivery (or per your contract) with a short, polite email.
What to include on an invoice
Your business details
Include the name you trade under, your address, and a contact email or phone number. Sole traders who use a business name may need to show their own name and an address where legal documents can be delivered — check GOV.UK invoicing guidance if you bill UK clients.
Client details
Bill the legal entity or person responsible for payment. For companies, confirm the registered name and billing address — especially on larger projects where finance teams process invoices.
Invoice number, dates, and reference
- Invoice number: Use a unique, sequential reference (for example
INV-2026-014). - Invoice date: The date you issue the invoice.
- Due date: When payment is expected (derived from your payment terms).
- Optional reference: PO number, project name, or contract reference if the client requires it.
Line items and descriptions
Describe work in plain language. Weak descriptions like “services” slow approvals. Strong descriptions explain what the client received:
- “Website homepage design — revision round 2”
- “Consulting session — 4 May 2026 (4 hours)”
- “Monthly SEO retainer — May 2026”
Totals, tax, and currency
Show subtotal, any VAT or tax if applicable, and the total amount due. If you are VAT registered in the UK, include your VAT number and show VAT separately where required. Do not charge VAT unless your business is registered and the supply is taxable.
Payment instructions
State how to pay: bank transfer details, payment link, or other method. Ask clients to use the invoice number as the payment reference so you can match incoming payments quickly.
Payment terms explained
Payment terms define when money is due. Common examples:
| Terms | Meaning | | --- | --- | | Due on receipt | Pay as soon as the invoice is received | | Net 7 / Net 14 / Net 30 | Pay within 7, 14, or 30 days of the invoice date | | 50% deposit, balance on completion | Split billing for larger projects | | End of month (EOM) | Pay by the last day of the month |
Put terms on every invoice and in your contract or proposal so there is no ambiguity. If you work internationally, state the currency (GBP, USD, EUR) explicitly.
Late payment clauses (statutory interest, fixed compensation in the UK for B2B debts) can be referenced in your terms — this is general information, not legal advice; speak to a professional if you need contract wording.
How to send a professional invoice
- Check the details — client name, amounts, dates, and line items match what was agreed.
- Export a PDF — most clients expect a PDF attachment or a secure link.
- Write a short email — state that the invoice is attached, the amount, the due date, and how to pay.
- Send to the right person — project lead plus accounts payable if needed.
- Keep a copy — store the sent invoice and date for your records.
Example invoice email
Subject: Invoice INV-2026-014 — May brand design work
Hi Sam,
Please find attached invoice INV-2026-014 for the May brand design deliverables we agreed.
The total due is £1,200.00, with payment due by 4 June 2026. Bank details are on the invoice — please use the invoice number as the payment reference.
Happy to answer any questions.
Thanks,
Alex
Chasing late payments
Late payments drain time and cash flow. A practical sequence:
- A few days after the due date — friendly reminder assuming oversight.
- One to two weeks overdue — firmer reminder with invoice number, amount, and due date restated.
- Further delay — phone call or video call with the decision-maker; pause new work if your contract allows.
- Serious delinquency — escalate per contract; consider debt collection or legal advice.
Tone matters. Factual, calm messages protect relationships while showing you run a professional business. InvoiceFeed’s free overdue reminder generator helps draft polite follow-up wording.
Tools to make invoicing faster
Spreadsheets work for your first few invoices. They become painful when you repeat client details, hunt for invoice numbers, and lose track of who has paid.
Invoicing software typically helps you:
- Save clients and reuse billing details
- Auto-increment invoice numbers
- Generate PDFs with consistent branding
- Track draft, sent, viewed, and paid status
- Send payment links where online payments are enabled
InvoiceFeed is built for freelancers and small businesses that want simple invoicing without full accounting complexity. Start with the free invoice generator, then create an account when you want client records and invoice history in one place.
Common mistakes to avoid
- Vague line items that finance teams cannot approve
- Missing due dates or payment instructions
- Reusing invoice numbers
- Sending to the wrong billing contact
- Adding VAT when you are not VAT registered
- Forgetting to invoice until months after delivery
Next steps
- Use an occupation-specific invoice template as a starting point
- Read UK VAT invoice requirements if you bill VAT-registered UK clients
- Try InvoiceFeed free when you are ready to organise client billing beyond one-off PDFs