While the UK doesn't have a single "Invoice Act" that dictates exact requirements, there are legal standards that invoices must meet for tax purposes and contract enforcement. Understanding these requirements protects your business and ensures you get paid.

HMRC requires that invoices contain sufficient information to clearly identify the transaction. For VAT-registered businesses, additional requirements apply under VAT regulations. Even if you're not VAT registered, maintaining proper invoicing standards is essential for your tax records and professionalism.

Beyond tax compliance, a well-constructed invoice forms part of the contract between you and your client. If a dispute arises, your invoice serves as evidence of what was agreed and owed.

VAT vs Non-VAT Invoice Differences

The requirements for your invoice depend significantly on your VAT registration status.

If you're NOT VAT registered:
Your invoices are simpler. You must not charge VAT, and you cannot include a VAT number. Many freelancers add a note stating "Not VAT registered" to clarify this to clients. Your invoice should show total amounts without any VAT breakdown.

If you ARE VAT registered:
You must issue VAT invoices that include specific additional information. There are two types:

  • Full VAT invoices — Required for supplies over £250 (including VAT)
  • Simplified VAT invoices — Permitted for supplies under £250

Full VAT invoices must include your VAT number, the VAT rate applied, the amount of VAT charged, and the total including VAT. We cover this in detail in our VAT Invoice Example UK guide.

💡 Practical Example

Tom is a freelance developer earning £45,000 per year — below the VAT threshold. His invoices show a simple total of £500 for a project. When his annual turnover exceeds £90,000, he'll need to register for VAT and start issuing VAT invoices showing £500 + £100 VAT = £600 total.

Your Business Details

Every invoice must clearly identify who is requesting payment. Include:

Business name: If you're a sole trader trading under your own name, use your full name. If you have a trading name, include both: "John Smith trading as Smith Design".

Address: Your registered business address. For limited companies, this must be your registered office address. For sole traders, typically your trading address.

Contact information: Email address and phone number. This helps clients reach you with any queries that might otherwise delay payment.

Company registration number: If you're a limited company, you must include your Companies House registration number.

VAT registration number: If VAT registered, this must appear on every invoice. Format: GB 123 4567 89.

Bank details: While technically payment information, it's standard practice to include your bank name, sort code, and account number with your business details.

Client Details

Accurately recording your client's details serves multiple purposes — it ensures the invoice reaches the right person, helps with your record-keeping, and is essential if you ever need to pursue payment legally.

Required information:

  • Client's legal business name (check spelling carefully)
  • Billing address
  • VAT number (if you're claiming reverse charge or zero-rating)

Recommended additions:

  • Contact person's name and email
  • Department (for larger organisations)
  • Purchase order number (if provided)

For corporate clients, always ask during onboarding: "What name and address should appear on invoices, and do you require a purchase order number?" Getting this right upfront prevents delays.

Line Items and Descriptions

The body of your invoice describes what you're billing for. Clear, specific line items reduce queries and speed up payment approval.

Essential elements for each line:

  • Description of the service or product
  • Quantity or time (hours, days, units)
  • Unit price
  • Total for that line
  • VAT rate applied (if VAT registered)

Writing effective descriptions:
Be specific enough that anyone reading the invoice understands what was provided. Instead of "Consulting", write "Brand strategy consultation, 2-hour workshop with senior team, including follow-up recommendations document".

💡 Poor vs Good Line Items

Poor: "Website work - £2,500"

Good: "E-commerce website development - 5-page Shopify store including product setup (50 products), payment integration, and responsive design - £2,500"

Reference project names, dates, or deliverable titles that match what was agreed in your quote or contract. This creates a clear audit trail.

Payment Information

Make it as easy as possible for clients to pay you. Include comprehensive payment details:

Bank account details:

  • Bank name
  • Account name (exactly as it appears on your account)
  • Sort code
  • Account number
  • IBAN and BIC/SWIFT (for international payments)

Payment terms:

  • Due date — always state a specific date, not just "Net 30"
  • Accepted payment methods
  • Late payment interest statement (optional but recommended)

Reference requirements:
Ask clients to use your invoice number as the payment reference. This makes reconciliation straightforward when payments arrive.

Many freelancers now include online payment links (PayPal, Stripe, bank payment links) which can significantly speed up payment — clients can pay immediately rather than scheduling a bank transfer.

Common Mistakes

These invoicing errors can delay payment or create compliance issues:

Charging VAT when not registered: This is illegal. If you're not VAT registered, you cannot charge VAT or include a VAT number. The extra money doesn't belong to you — it belongs to HMRC.

Missing invoice numbers: Every invoice needs a unique, sequential number for your records and the client's. Skipping this looks unprofessional and makes bookkeeping difficult.

Vague dates: "January 2026" isn't a proper invoice date. Use specific dates: "10 January 2026".

Incorrect client details: Misspelling company names or using outdated addresses often sends invoices to spam or the wrong department.

Missing purchase order numbers: Many corporate clients cannot process invoices without a PO reference. Check this before invoicing.

Ambiguous currency: If you work with international clients, always specify currency: "GBP 500.00" not just "500".

Requirements Checklist

Use this checklist to ensure your invoices meet all UK requirements:

✅ UK Invoice Requirements Checklist

Your Details:

  • ☐ Business name or your name
  • ☐ Trading name (if different)
  • ☐ Business address
  • ☐ Contact email and phone
  • ☐ Company registration number (if limited company)
  • ☐ VAT number (if VAT registered)

Client Details:

  • ☐ Client's legal business name
  • ☐ Billing address
  • ☐ Contact person (recommended)
  • ☐ PO number (if required)

Invoice Details:

  • ☐ Unique invoice number
  • ☐ Invoice date
  • ☐ Due date
  • ☐ Clear service descriptions
  • ☐ Quantities and unit prices
  • ☐ Subtotal
  • ☐ VAT amount and rate (if applicable)
  • ☐ Total amount due
  • ☐ Currency specified

Payment Details:

  • ☐ Bank name, sort code, account number
  • ☐ Payment reference
  • ☐ Alternative payment methods (optional)

Following these requirements ensures your invoices are legally compliant, professionally presented, and likely to be paid promptly. When in doubt, include more detail rather than less — it's always easier to simplify later than to answer queries about unclear invoices.

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