Freelance Invoicing Guide 2026: The Complete Basics
Updated 2026 · 8 min read · General information, not accounting or legal advice
Invoicing is the one thing every freelancer has to get right — and the one thing nobody teaches you before you start. A badly written invoice means late payments, lost VAT deductions, and in some countries, fines. This guide covers the essentials: invoice numbering, VAT and sales tax, and the late payment penalties you can charge when a client drags their feet.
What makes an invoice legal?
Rules vary by country, but a valid invoice almost everywhere must include:
- Your full business details: name, address, and tax ID / VAT number where applicable.
- The client's details: name and address (plus their VAT number for B2B invoices in the EU).
- A unique invoice number (see below) and the issue date.
- A clear description of the work, quantities and the agreed rate.
- The total amount, with tax shown separately when you charge it.
- Payment terms: due date, late payment penalty, and how to pay.
Invoice numbering explained
Invoice numbers exist so you and your client can track payments and so tax authorities can audit you. The rules are simple:
- Must be unique and sequential. Never reuse a number, even after a cancellation.
- No gaps are fine (unlike some older rules), but reusing or skipping numbers randomly looks suspicious to auditors.
- Use a format that helps you. Popular patterns:
2026-001, INV-2026-0142, or ACME-0007 per client.
- One invoice = one number. If you correct an invoice, issue a credit note referencing the original number instead of editing history.
💡 Practical tip
Start numbering at 0001 each calendar year (e.g. 2026-0001). It makes year-end reporting and tax filings much easier — and clients immediately see how long you've been working together.
VAT and sales tax for freelancers (US, UK & EU)
VAT (Europe) and sales tax (US) are not the same thing as income tax — you collect them on behalf of the government. The key facts:
| Region | What applies | When you must register |
|---|
| EU | VAT (e.g. 20% UK, 20% FR, 19% DE) | Over the local threshold (e.g. €10,000 in France, £90,000 in the UK for most services) |
| UK | VAT (20% standard) | When taxable turnover exceeds £90,000 (2026 threshold) |
| US | State sales tax (0–10%+ depending on state) | Depends on state "nexus" rules — most service freelancers never collect it |
- B2B in the EU is usually reverse-charged: you don't add VAT if the client is a VAT-registered business in another EU country — they self-assess. Put "Reverse charge" on the invoice.
- Under the threshold, don't add VAT — and don't show a VAT line you can't remit. It's a red flag for tax authorities.
- If you're VAT-registered, always show your VAT number, the rate, the net amount and the tax separately.
Late payment penalties: what you can charge
Late payment is the #1 freelancer complaint. Most jurisdictions give you legal grounds to charge interest and penalties:
- EU & UK: the Late Payment Directive allows statutory interest (usually base rate + 8 points) plus a fixed recovery fee (€40 / £40 for most invoices) after 30 days past due.
- US: no federal rule — your contract governs. Common practice: 1–1.5% interest per month and a late fee after 15–30 days, stated on the invoice.
- Always put the penalty on the invoice itself. If it's not written, you can rarely enforce it.
📌 Late payment wording you can copy
"Payment due within 30 days of the invoice date. A late payment penalty of [X]% per month (or statutory interest under the Late Payment Directive) applies to any amount received after the due date, plus a fixed recovery fee of €40."
Payment terms that actually get you paid
- Ask for a deposit (30–50%) before starting — it filters out bad clients early.
- Prefer 14 days over 30 for new clients, then relax once trust is established.
- Offer card or instant bank transfer options — friction is the enemy of payment.
- Send a friendly reminder 3 days before the due date, not after it.
- Stop work on overdue invoices — politely, and with the contract clause to back it up.
Checklist before you send an invoice
- Unique invoice number, correct date and payment terms ✔
- Your details and the client's details complete ✔
- VAT / sales tax correct — or explicitly not applicable ✔
- Total matches your quote or contract ✔
- Late payment penalty stated ✔
- Sent as PDF from your business email (never a plain email body) ✔
Tools that make invoicing painless
You don't need to start with paid software. Use our free VAT calculator to check amounts, and a simple spreadsheet or free invoicing tool for your first invoices. Upgrade to dedicated invoicing software only when you're sending more than a handful per month.
In summary: number invoices sequentially, know your VAT/sales tax position, put your late payment penalties in writing, and never let an invoice go out without a due date.