What an Invoice Must Contain: Legal Requirements for Freelancers
An invoice is a payment instruction, not a receipt. Anything that forces accounts payable to email you a question adds a week to your payment date. A complete invoice carries seven core fields — plus tax registration and payment details that vary by jurisdiction.
Last updated 2026-09-17.
The seven mandatory fields
These are required in virtually every jurisdiction for an invoice to be legally valid and payable:
- 1
Unique sequential invoice number
No gaps, no duplicates. See Invoice Numbering Best Practices.
- 2
Your legal or trading name + contact details
Address, email, phone. If you trade under a different name than your legal entity, show both.
- 3
Client's name and billing address
The legal entity you are billing, not just your day-to-day contact. Include their VAT/GST number if they are in the EU or another jurisdiction that requires it for reverse charge.
- 4
Issue date and due date
The issue date starts the payment clock. The due date ends it. Write the actual calendar date (e.g., “05 Sep 2026”), not “Net 30” alone.
- 5
Itemised description of goods/services
Each line: description, quantity, unit price, line total. Be specific enough for the client to match against the work they approved.
- 6
Tax treatment shown as its own line
Rate (e.g., 20%), label (VAT, GST, Sales Tax), and the tax amount calculated on the discounted subtotal. If zero-rated or exempt, state that explicitly.
- 7
Total amount due in the payment currency
Unambiguous currency code (GBP, USD, EUR) and the final figure the client must pay.
Tax registration number (when required)
If you are registered for VAT, GST, or sales tax, your registration number must appear on the invoice. In most jurisdictions the client cannot reclaim the tax without it.
- UK VAT: GB followed by 9 digits (e.g.,
GB123456789) - EU VAT: Country code + number (e.g.,
DE123456789) - Australian GST: ABN (11 digits)
- Indian GST: GSTIN (15 characters)
- Canadian GST/HST: Business Number + RT0001
- US Sales Tax: State-issued permit number (format varies by state)
If you are not registered, do not invent a number. Charging tax you are not authorised to collect is a serious offence.
Payment terms that belong on the invoice
- ✓Due date: Calendar date, not just “Net 14”.
- ✓Late-payment terms: Rate, basis (simple/compound), grace period, flat fee if any. Example: “Payment due within 14 days. Late payments carry 8% annual simple interest after a 7-day grace period.”
- ✓Payment methods accepted: Bank transfer (with full details), card link, etc.
- ✓Currency: The currency you expect to be paid in.
Jurisdiction-specific requirements
United Kingdom (VAT)
VAT invoices require: your VAT number, client VAT number (if B2B), tax point (usually issue date), rate per line or per invoice, and total VAT shown separately. Simplified invoices (≤ GBP 250) can show less detail.
European Union (VAT)
EU VAT Directive (2006/112/EC) mandates: both parties' VAT numbers, sequential numbering, issue date, description, quantity, unit price net of VAT, applicable rate, VAT amount, and total. Reverse-charge invoices must state “Reverse charge” and cite the relevant directive article.
Australia (GST)
Tax invoices (≥ $82.50 AUD) require: ABN, “Tax invoice” title, date, supplier and recipient identity, description, GST amount (or statement that GST is included), and total. Recipient identity optional if < $1,000.
India (GST)
GST invoices require: GSTIN of supplier and recipient, invoice number (max 16 chars, sequential), date, HSN/SAC codes, description, quantity, unit, taxable value, rate (CGST/SGST/IGST), tax amount, place of supply for inter-state, and signature/digital signature.
United States (Sales Tax)
No federal invoice mandate. State rules vary. Generally: seller and buyer identity, date, description, amount, tax shown separately (rate + amount), and seller's permit number. Some states require “Sales tax” label; others accept “Tax”.
Canada (GST/HST)
Tax invoices (≥ $30 CAD) require: supplier's Business Number, “GST/HST” registration, date, buyer name, description, total amount, and GST/HST amount shown separately or a statement that tax is included.
How the Invoice Generator maps to these requirements
| Requirement | Generator field |
|---|---|
| Invoice number | Invoice number |
| Your name + contact | Business name, Email, Phone, Address |
| Tax registration | Tax or company ID |
| Client name + address | Client name, Client address |
| Issue / due date | Issue date, Due date |
| Line items | Description, Qty, Unit price |
| Tax line | Tax label, Tax rate |
| Total due | Summary panel (auto-calculated) |
| Payment details | Payment details textarea |
| Late-payment terms | Notes & terms textarea |
Related guides
- How to Create an Invoice: Step-by-Step Guide
- Invoice Numbering: Best Practices for Freelancers
- Tax Exclusive vs Tax Inclusive: The Mistake Everyone Makes
- Charging Tax to Overseas Clients: Place of Supply Rules
This guide summarises common invoice requirements. It is not legal or tax advice. Requirements vary by country, state, and tax scheme. Verify with a qualified professional in your jurisdiction.